It seems the worry for my three adult children and their families is situational. When they are not settled, or going through a rough relationship, or their own job stress I have laid awake at night fretting about them. Couldn't help myself.
But some situations just need to work themselves out, and sometimes your children need you and your advice, or time, or babysitting services. There were times when one son needed a bit of a shaking (not literally, but I was tempted) to get his act together. You can only do so much and I try to not let it keep me up at night.
Helping them to help themselves is the goal for us. They are all very capable young adults with good partners. I think we are always learning, and hopefully the advice from us older parents with more life experience is taken into consideration.