When people say "Let it go," what they really mean is "Get over it," and that's not a helpful thing to say. It's not a matter of letting go - you would if you could. Instead of "Let it go," we should probably say "Let it be"; this recognizes that the mind won't let go and the problem may not go away, and it allows you to form a healthier relationship with what's bothering you.
Jon Kabat-ZinnThe mind that has not been developed or trained is very scattered. That's the normal state of affairs, but it leaves us out of touch with a great deal in life, including our bodies.
Jon Kabat-ZinnIn any given moment we are either practicing mindfulness, or defacto, we are practicing mindlessness.
Jon Kabat-Zinn