Why can't I seem to concentrate on one project at a time?

I am an aspiring swe, and now that I graduated, I have tons of free time that I wish to make use to its most optimal. I really want to be a game dev, so I bought stephen's unreal engine multiplayer course and have been following it religiously. But after multiple setbacks like project corruption, I managed to finish the first milestone of that course. But I lost motivation halfway through and decided to take a break by redesigning my portfolio into a cool pokemon javascript game-ish design. Yet after a while I felt burnt out again and decided to grind leetcode as I want to break into FAANG in a few years time.

What is going on? Do I have like undiagnosed adhd or something? Why cant I seem to just grit my teeth and finish something once and for all without burning out so quickly? It is very frustrating looking back at past few months with unfinished projects