Letting go is the same thing as holding on.  Letting go of the way you thought things should go, the person you thought someone would be, the way you pictured your life at this age, the idea of a memory you play in your mind a million times just wishing to go back to it's sweet simplicity; we cling to these thoughts like oxygen to breathe and we tell ourselves -
This is safe.  This is right.  This is the only way things would be okay.

Letting go is the same thing as holding on.  Holding on to the details you had perfected in your mind - I would be happier, I would be richer, I would be in love, I would be in shape.  I would have this person by my side, I would have time to do the things I love, I would have said this instead.  You say I would, I should, I could.  Assumptions, predictions and the way things would be contrasting against reality, the truth and the way things are.  You hold on to self-doubt and search for pain in order to prove to yourself you were right all along.  You shouldn't have gotten your hopes up, you should have settled for less, what's the point in even trying?
This isn't safe.  This isn't right.  Will things ever be okay again?

Letting go is the same things as holding on.  Letting go of your idea of perfection, the heavy weight of not good enough you hang on all of your words and actions, the shade you cast on all of the things waiting patiently in your life for you to recognize the light they're waiting to give you.  To let go of the things you have no control over - what people do and say, how much the world has changed, the time it's taking to find the person you see a piece of yourself in - in order to give yourself the ability to work with and create things out of the things you do have control over - taking care of yourself, enjoying the simpler pleasures of life, the smile you give to a stranger.
This seems safe.  This feels right.  Maybe things could be okay.

Letting go is the same thing as holding on.  Holding on to the high of accomplishing something you thought you never could, holding onto your pet sitting on the couch after a long, challenging day, holding onto the parts of yourself that get lost in a good song or the sudden captivation of the sun cascading off buildings as it sets in the distance.  Letting go is accepting the things and circumstances in this life that you cannot change.  Holding on is finding the power it takes to find peace and joy in the things that you can.  Letting go in a state of appreciation for the heavy and what it's taught you in order to hold on to and accept the light and your part in choosing to stay focused on it.
This is safe.  This is right.  It turns out things we're okay all along.