Start with what gets you most jazzed in your life. Find another person who enjoys the same thing. Engage in that activity with this "friend" and see if you are both drawn towards the idea of dating.
I wish I could've had more time with my kids. I wish my then-wife had agreed to 50/50 shared parenting. I wish my ex-wife would be a more collaborative parent. But even as I wish about these things, even as I can feel regret about the lost time, I am HAPPIER NOW THAN I HAVE EVER BEEN IN MY LIFE.
Don't let any of your shit fester and darken your experience of life. Life is too short to be compromising with someone you don't love 100%. Oh, and it's your responsibility to love them at 100%. It is your intention and actions, for the rest of your life, that will determine the success of your next relationship.
It was not fair what happened, and in many ways, my ex-wife was the architect and builder of the divorce.
In this day I release my ex-wife. I release my two lovely children from any frustration I have at not being able to book time on their busy teenager calendars. I release myself from my expectations of where I would be at this point in my adult life.
I have approached dating as a process to identify, qualify, and ultimately partner with a single woman. The dating part is essential, but dating is not the goal. Sex is essential, but sex, also, is not the goal. Working to identify and explore a combination of these three factors, is how I am navigating my approach to finding my next long-term relationship.
My ex knew I would not sue her for 50/50 custody. She didn't want to lose 50% of the time with her kids. 30% sounded almost palatable. Painful, but well worth the freedom she imagined just ahead, as she headed towards becoming a single mom.
Don't give up. Just because all of your previous relationships have failed, does not mean that the next date might be The One.