Sense of Loss

There are times when one gets a sense of loss.
Loss of something that would never return to the same as before.
In life, we all lose a little of something.
Time moves forward and can never be turned back.
I have this sense of loss.
A loss that has happened due to time.
But I can't explain what the loss is.
Neither can I explain the frustration I feel sometimes.
Just a sense of loss.