I try my best to stay on good terms with my exes. I wouldn't say we always end up friends but we can at least see each other and have a decent conversation.
However, it's different with one person. She's my first love, she's with someone else. And lots of things used to eat at me about them, about us but now she just frustrates me. I want to tell her to get the fuck out of my life and that I get opportunities too, I just choke every time.
It's been this way for years. It started when we were together, and I eventually came to the conclusion that I didn't want to tell her to fuck off because I was so in love with her.
But now we're not together. It's so simple for me to just say fuck you and fuck off, but I don't, I just stay there letting shit come up until I eventually get frustrated and I'm the one who ends up sad. Why is it that after being so strong before and so able to just tell my significant others in past relationships "This isn't working, get away from me" I seem to be stuck? Why can't I find the strength and motivation to just tell her to leave me alone?
Your question starts with "I try my best to stay on good terms with my ex's" and it ends with "Why can't I find the strength to tell her to leave me alone?" And all I can discern from the middle of your question is that you are still in love with her.
Relationships with exes are complicated. And if you are still in love with her (which it seems you are) then your "frustration" is probably more about unresolved sadness and hurt than it is about anger or irritation. Perhaps the struggle to tell her to leave you alone is because you simply don't want her to leave you alone.
First loves are unparalleled. Most of us remember all too well our first loves. Rarely, however, do we end up with them. There are, of course, some exceptions.
When it comes to lesbians and exes, things can get complicated. My rule of thumb is that couples need to separate for 90 days - having little to no contact after a break up and then resume contact from a new perspective, as two people who have been spending time living life apart. The separation allows you the space to create an identity outside of your relationship. The break gives you a chance to heal from the pain. It also gives you a chance to get out of habits you've formed as a couple - like calling her "honey," or touching her affectionately. These habits can be very difficult to break and lead to poor boundaries as friends, sending mixed messages.
If you take a 90 day break and still feel a strong desire for more than friendship, then it is probably in your best interest to not spend time with your ex because it will most likely fuel your thoughts and fantasies of reunifying. This is okay if she reciprocates the feeling, but often that is not the case.
So when it comes to saying "F off," my suggestion is that you start with a request for a 90 day break. Have no contact, at all, and see how that feels. Once the 90 days are up, assess how you are feeling and consider contacting her for a friendship. Consider your motivation for having this friendship and be sure your friendship is not a cover for your deep desire to get back together. These hidden agendas and hopes can cause a lot of emotional turmoil and lead to reactions that seem disproportionate to the situation.