This.

Stop romanticising unhealthy relationships. Stop thinking you can change someone. You' can't.  They need to change for themselves. Stop romanticising the idea of you two being together some day. If it isn't happening now, let it go. No more pouring your heart out to someone who gives you little to no reciprocation. Find someone who values your long letters and passionate attempts. This person will reciprocate, with twice as much fire.