I'm pretty sure this post is allowed but if not, then i'm sorry. Also i hope i added the right 'flair'. TLDR at the bottom since i ended up ranting.

I'll preface this by saying that i'm not diagnosed with BPD, but i have all of the symptoms you'd normally see on a list. All of them, and they've been here for years. I've already contacted my psychiatrist about it and basically gave her a letter about it, so I don't need advice on how to get diagnosed (i don't live in the US or any english speaking country, so chances are, whatever applies there won't apply where i live).  
I just need advice on how to live with this crap.

I can barely deal with the constant changes in persona and feelings about things, the inability to have normal relationships (i have a lot of friends actually, but i'm always masking around them), i unintentionally become toxic because i manage to turn every convo to be about me and unintentionally vent to people, i can't deal with rejection and i can't even perceive it properly and its straining my relationship with my best friend. You probably know the deal, but i can't handle when she doesnt reply (and her special skill is leaving me on delivered for more than a day, then only messaging me when she needs something) or when she hangs out with others and comes up with some excuse for not inviting me.

Same thing happens with others- just not at the same level. But i always go from completely depressed about it, to pissed off and thinking of ways to make them feel horrible about it, to feeling guilty. To my credit i manage to sort of keep this in check (there's been a lot of times where i've considered hurting myself just for my friendss to 'regret' not appreciating me, but i haven't done that because that's just manipulation). 

All of these dumb issues are just making me feel more and more depressed about life when i'm not in some sort of angry, anxious or manic state. At the end of the day i always just feel like crying. I can't see the point of anything - i don't know how to change this because it's just the way i see the world. I try to appreciate the little things, but it's hard when your brain just sees the extremes.

TLDR; i am not diagnosed with BPD, but i have all the symptoms, and i don't know how to deal with it anymore. Everything basically feels hopeless. i go from one extreme to another too quickly and i'm scared that one day i won't be able to control my own actions because of it anymore, as cringe as that might sound.