This is because, even if you don't want to end up like this, your mind likes what its doing for now, because it's easy and nice.
>become too used to comfort zone
>predict you need to do something to keep this comfort zone running, but you don't really like doing it (working, studying, etc)
>start doing it
>your subconscious mind communicates with you: It tells you to stop doing that by causing you feel bored, tired and exhausted. This is because it prefers you to skip the task and go back to the comfort zone, even if this dooms you in the future.
Basically subconscious prefers easy present, hard future to hard present, easy future.
So it will make you run away and avoid the problem until nothing can be done about it, then just endure it or do something else.
tl;dr: You don't really enjoy doing that activity, you just do it because you need to do it, or because you are forced to.
Subconscious knows about it and it tells you the truth.
I'm completely mind blown.
You've summed up a problem which I could never solve in just a few lines.