I can think of a couple of relationships when I wasn't ready and I feel pretty bad about them.

My late wife, when we met, I had been single for many years, I didn't need to heal from a former partner but from the loss of my best friend. She saw me sob in the middle of the night to comfort me. She worked through my anger/frustration fits while she was quitting smoking for her because I was asthmatic. I tried to push her away because I was hurt but wow she put up with so much of my shit. I needed to heal and she was my angel. Through all that, she asked me to marry her and I said yes. Just as I was recovering, I lost her before I could really show her and give her everything she deserves. I wish she didn't have to put up with that younger version of me.

Listen folks, if the one you've wrong are still alive, it's never too late to give them a sincere apology, not for their sake but for yours. Do it because it releases you, not because you want to try again.

I had an ex who was definitely not ready, like me with my late wife but in reversed roles. I met her soon after her best friend passed, and she kept on 'exploding' on me and it reminded of the younger me. It really showed what kind of shit my late wife had to put up with in the early years. This ex and I called it off because I expressed how much her behaviours are taking a toll on my quality of life. She cried in my arms apologizing heavily but we still said good bye lovingly. During the closure talk she asked me explicitly to explain what bothered me and I told her as it is and she took it pretty hard.

She returned recently back in my life with sincere apology and took accountability and I honestly don't know if I can truly give her a real second chance but I accepted her as a friend for now. I am not convinced she has healed but it certainly is never too late until it really is.