I don't know what it is, but I've done this in both friendships and relationships. 

Any time I have a perfectly happy, normal, great relationship with someone, my brain starts telling me to push them away. I am amazed that I still manage to sustain the few long term friendships  as long as I have. 

I have self sabotaged many relationships and friendships. I've stressed people out with this as well as myself. It hurts me to push people away, but it's almost like a force in my brain takes over and is telling me that it's the right thing for them. Almost like I have to protect them from myself? 

I completely understand this is an irrational thing to do, and i am told this all the time. Yet my brain insists it's what I need to do. 

If I feel my mental health start going downhill, I get scared and immediately try to shut people out because I have this irrational thought that my mental health problems hurt people. But this process completely contradicts the purpose, because I end up making myself feel so much worse by isolating myself.

I'm asking for advice on this because I got a new partner for the first time in a year and he's been wonderful. The past few months with him have been incredible. I couldn't ask for a better person to be with.

 I recently noticed myself overthinking a lot and worrying that I could hurt him with my mental health. I *always* do this when I start dating someone and I hate it. I want to break out of this habit of mine because I don't want to sabotage this one. He also struggles with mental health and understands and wants to be here for me. How do I let him do that? I have no idea how to just relax and let myself be happy.