Letting go is a big concept in Yoga. It is usually termed releasing attachment, non-attachment, or non-grasping (Aparigraha in the Yoga Sutras).
Most of us have attachments to material or external things and we frequently have them removed from us against our will, resulting in a sense of loss or suffering. When our goals aren't reached. When our children no longer follow our wishes. When our job is lost. Or, the ultimate challenge, the death of a loved one.
We really and truly can never HAVE anything, so it is a misconception that attachment is even possible. It is actually impossible. We could even say that we really only borrow our body for a century or so. When we acknowledge how temporary everything is, we can really enjoy what and who we have while they are with us, and we can grieve and move on when they are taken away.
When you live fully in your intentions and let go of the results. You can live a life of passion and purpose in a way that isn't devastated by all of the eventual set-backs and obstacles.
As teachers, Saffron and I are always discussing the ways that we can make Yoga accessible without imposing our own idea of how things need to be. We all face this difficulty as we seek to bring a positive influence into the lives of others (kids, employees, co-workers, family) without imposing our personal agenda that is often cluttered with our own personal blind spots.
Non-attachment is not without passion, we can be very passionate about inspiring others. Non-attachment asks us to look at how we "expect" it to turn out.
Try letting go of how it is supposed to be. Correct your course, but also correct your map occasionally. That large boulder might not be on your map but it is there now. Why crash against it or rail against it for being there? Walk around and let it go..