I submitted a very similar post to the suicide watch subreddit, and admit that i received less comments than expected. Perhaps this is because the subreddit concerns a great variety of obstacles that people face in their lives. 

Perhaps it is better to submit this post here, as I have BPD and people here are more familiar with the phenomena of splitting and idealization ...

anyway, what's happening is this. There is someone I love who I met a year ago. When I met her I was 17 and she is in her 20's. I started feeling this way for her early on, but waited until I was 18 to say anything of this. There are more things that occurred in this time, but I will not overcomplicate things. 

I often have the compulsion to give into suicide. For a long time I was able to motivate myself away from this by imagining dating her, living with her, and helping her to achieve her goals, as she is also mentally ill and faces similar obstacles ...

Well, I recently admit these feelings to her, and she says to me that she does not feel this way about me and never will. 

Well, now I feel great pain. I am a very eccentric person and so is she to some extent; the people I feel I am compatible with and can be totally honest with are extremely few. The narrative in my mind is that there is no one similar to me in this world, and that I will spend my time here blocked off from others with no opportunity for strong friendships and romantic relationships. 

I admit I used this idealized future as a crutch, and in the knocking out of it from under me, I now feel the despair I avoided now coming at me in full force, and that I really have no reason to live.

This is what I am facing right now, and I hope I have explained it coherently, perhaps better than I did in the other subreddit. Advice is greatly appreciated.