It works both ways remember... you have a life w/o kids now too. How are you planning to use it? And I think it is natural to feel sad when you look back and wonder how things might be if.... bad trap! Stay in the present and remind yourself that things worked differently - for a reason- and it was never going to go in that direction or it would have do so. No fault - no blame - just the facts.
So I see you helping others here, and spending time with your kids, what else are you doing?