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-ZinnMindfulness practice means that we commit fully in each moment to be present; inviting ourselves to interface with this moment in full awareness, with the intention to embody as best we can an orientation of calmness, mindfulness, and equanimity right here and right now.
Jon Kabat-Zinn