There are moments where I enter a kind of dejection, knowing what I'm capable of achieving but not having reached it and not having the motivation to even try.

I'm sure this stems from a self-centered or ego-centric perspective we all have of life, in which we are the main character and everything around serves us. And even though from a certain perspective the world does revolve around us, it leads to moments of dejection when we don't live up to our expectations.

I say this perspective where the world revolves around us is true because from an experiential point of view the whole universe is the single experience we are having in this moment. We can't possible know that anything else exists though we can believe it to exist. Our knowledge is limited to our sense and thought experiences and that makes life very self-centered.

But if the self can be seen as just a collection of experiences that arise with the perception that these are "myself," then we can have moments where life is centered around the unfolding present but not around a self. I've encountered this state several times and it is quite peaceful and nourishing.

I think in the moments where I'm feeling like this I need to recognize where the self-identification is arising, note it, and watch it disappear. Perhaps, that will leave the situation unchanged but at least I will feel better.