Sometimes, the hardest thing for a parent is to step aside and allow someone else to be there for your child. Whether it's a skinned knee, an emotional upset, or a classic life transition, you can't always be there for every event when s/he needs support – and you shouldn't be, either.
As much as you think you want to be the one they turn to, it actually empowers your child to learn to rely on other people. Part of the skill is in recognizing when they need help, and part of it is in learning to ask for it. We parents tend to swoop in before it's clear that our child really needs help at all!
So letting others support your child through life's challenges actually fosters independence and self-reliance.
This is true when co-parenting, as well. We moms tend to do too much, and make it hard for our kids' dads to do enough. Sometimes, we need to step back and give Dad a chance to be the parent their child needs the most. It's difficult. It can require a lot of sitting on your hands. But it's a gift to the entire family.