How to Maintain a Relationship
One way you can maintain your relationship is by asking questions as your partner talks about their feelings to show your interest. Avoid starting conversations with typical questions like “How was your day?” since they usually end up with shallow answers like “Fine” that won't give you any insight about your partner's thoughts and feelings. As your partner opens up to you, show them you're truly listening by occasionally paraphrasing what they are saying. You might not agree with everything they say, but you should show them respect by allowing them to fully explain their views. Always accept your partner for who they are and don't try to change them, since that will only cause frustration that will weaken your relationship.
Do not try to change your partner. Accept that you can only change yourself, not your partner. This is perhaps the hardest but most important tenet of a solid relationship. You should never enter a relationship with the plan to "fix" your partner. You need to accept the fact that your partner may never change, and be okay with that. To do otherwise is a guaranteed way to frustrate yourself and alienate your partner. You may support your partner to make positive changes in their life. But you should never try or need to fundamentally change them. If you cannot accept your partner for who they are, you either need to set boundaries to avoid getting hurt or leave the relationship entirely. Understand that men and women are different. Or for that matter understand that different men and different women are different. Do not unfairly hold your partner up to the standards of an old relationship or of an ideal one. Do not control your partner. We all know that violence is not an acceptable way to control partner. But know that using guilt or shame is just as damaging. Guilting or shaming to control your partner is emotional abuse. Do not attempt to control your partner. This is an extension of "Do not try to change your partner" step. If you cannot handle compromise then leave the relationship, do not try to control or change your partner to make it work. Support their interests. You do not have to share your partner's every hobby. But you should listen to your partner when they talk about their interests, and give them guilt-free time and space to pursue their interests. Don't minimize your partner's emotions. While not every emotion is desirable (for example anger, resentment, and frustration), they are all normal. If your partner is angry at something, do not criticize them for being angry -- that cannot be helped. What people are responsible for is how they express their emotions. Anger can be destructive or constructive. You may rightly criticize how emotions are expressed and ask that they be shared in a constructive fashion, but do not critique the emotion itself. Critiquing emotions can lead to your partner feeling guilty, defensive and emotionally withdrawn. A destructive expression of anger is to yell and throw things. A constructive expression of anger is to talk about one's anger feelings and reach a conclusion. Example: Do not say "Don't be mad" or "You shouldn't be mad". Telling your partner not to feel something is futile and hinders further communication. Your partner cannot help but be mad. Instead say, "I understand you are angry. Can you tell me calmly why?" and work together through dialogue to get to the root of the problem and come to an agreeable solution. Listen. Don't just nod your head and say "uh uh" but practice active listening. When practicing active listening you need to ask questions and paraphrase back important points to demonstrate your involvement and interest. You are never done learning about your partner, nor they about you, and learning starts with good listening. A good, deep relationship requires lifelong maintenance and effort, but the effort is worth it for the support, security and love from someone who really knows you. Respect each other. Listen when your partner talks. Respect your partner's opinion by allowing them to express it in full, even if you disagree. Take the time to really understand your partner's views by asking questions and attempting to paraphrase what they are saying to you. Get to the root of problems. Do not simply try to fix the symptoms, but when your partner or you is unhappy take the time to explore and understand what is the source of the problem and fix that. For example if your wife is mad that you spend too much time with the guys and doesn't want you to go out, you could treat the symptom and just stop ever hanging out with the boys, but this is not a healthy long-term fix. Instead you should explore the numerous reasons why she doesn't like you spending time with the guys. Ask questions and listen to her without judging to uncover her motivations. You may find that: A) She is jealous of other women at the bars you go to with the boys. Solution: Change the venue, or invite her to "drop by" and see that nothing unseemly is going on. B) She thinks you do not like to spend time with her and do not like her. Solution: Schedule regularly quality time with her, and verbally ensure her that you enjoy her company too. C) She thinks that your hanging out with the boys unfairly burdens her. This is especially true if you have kids, as your hanging out with the boys means that she is on solo baby duty. Solution: Offer to give her a day out with the girls too. And make sure you are not falling behind on household chores when you do go out. Anger is a waste of time. Your goal in a relationship is to build connections and work through problems together. Being angry may give you a sense of self righteousness, but it does nothing to move a relationship forward to a solution. Let your anger go, even if you are "right". Keep your fights clean. In the course of all relationships there will be disagreements. This is normal. But how you handle these disagreements reflects on the health of your relationship. Disagreements are not the time to air every grievance you have ever had. Disagreements are also not the time to "get even" with your partner by hurting them emotionally. Disagreements are a time to discuss your different views as they relate to the problem at hand and work towards a mutual solution. Make efforts to establish physical contact. In the early stages of a relationship expressing your love is natural and regular. You can not wait to hold their hand, steal a kiss or more. But after a few years or decades, even the steamiest relationships tends to cool. Hand holding, back rubs, and kisses do not just happen, especially if you have kids. Make time for these things. Make a conscious daily effort to establish loving physical contact with your partner. Say "Thank you". Daily express your appreciation for your partner. Even if your partner is just doing their "fair share", it is still important to thank them. When your husband does the dishes say, "Thanks for doing the dishes". When your wife puts the kids to bed say, "Thanks for handling the kids tonight." It seems silly but these little niceties go a long way for making your partner feel appreciated, and feeling appreciated can head off resentment or anger stemming from "not feeling appreciated". Say "please". Do not demand from your partner. Ask nicely, even if it is something you expect them to do. Instead of saying "Get the kid juice", say "Would you please get the kid juice?" Saying "please" changes a demand to a favor and helps establish a respectful cooperative relationship. 
Do not try to change your partner. Do not control your partner. Support their interests. Don't minimize your partner's emotions. Listen. Respect each other. Get to the root of problems. Anger is a waste of time. Keep your fights clean. Make efforts to establish physical contact. Say "Thank you". Say "please". 