Can't add much to all the good advice hear. Wanted to send ESH. I do think as mothers we see our children as different from a spouse. But all learning comes from consequences - do something and there is a result - you do something different there is a different result.
But as always here, your call for help seems to be more about you. What are you doing for yourself in all of this. I could offer many examples of what to with an adult child but none of it would help unless you have settled things with yourself. As a parent I have made some decisions I felt bad about but knew in my heart that it what necessary for the other to grow. So everytime I miss one of my kids or wish I had done things differently I always can remind myself that in my heart I made this decision and it is ok.
The harder part has been taking care of me.