It sounds to me that you don't want to quit ridding, but are just discouraged. I for one can empathize with you. I have been having a Low HR problem and can't seem to find the answer. From 165 to 123 for a long time. Now it's back up to 135 as a Max sustainable HR. This has made a huge difference in my cycling, and is extremely frustrating.
I have been tempted to quit on many occasions, but I just got this new bike just before I got I went down and I want to get my money's worth out of it. In order to do that I need to ride for another 30 years, or until I get to 101.
Good luck and maybe take it a little easer on yourself. That's what I need to tell myself anyway.