Am I supposed to ride this out?

It's just a heart crushing feeling to have nothing but love for someone, feel it being returned for years, and then one day it randomly fades.

How much of the past matters in a relationship? Based on the past, it tells me I should hold my breath and ride this out. When I "retaliate" I feel like I'm betraying her. If I let my feelings take over and leave, I start to feel full of regret as time goes by. Maybe I'm supposed to know what I signed up for, that being with her isn't easy. I know she can't just be with any guy. She once asked me if I thought she was datable. I didn't answer that but my answer is no. My personality is the complete opposite of hers which is the only reason why we work together. But it's also because of that that we're starting to disconnect, or at least why she is and why I'm being hurt.

At this point she has stopped being considerate of my feelings and I have lost trust in her, which almost makes me feel like giving up on everything. But what if I'm not supposed to give up here, what If I'm supposed to be strong and fight where everyone else would have given up? Maybe that's what it takes to win her love, to make her really love someone. I know with her it isn't supposed to be easy. It's just when it comes time for me to prove myself, the pain is so much to bare and I end up folding to it, which will destroy us..

I honestly have no clue what I should do.