Doing minimal work but expecting good results.

I don’t understand why is this even a problem. knowing how easy it is to fix. All I have to do is simply just “start doing it” nothing is holding me back. Doing a homework for example, I will try my absolute best to do it at the VERY LAST moment just before the deadline and when I “finish it” I convince myself that I fully understand the topic. Then teacher asks me couple of questions about the topic and I just stand there like a dumbass I go back home pissed because I was (get this) expecting THE BEST out of myself. I want to major in computer science and this is my last year in school I don’t want be completely unprepared and want to stand out from others. Instead of practicing programming, doing homework or generally getting better at something I play videogames and watch Youtube videos, periodically telling myself “Yea I will do it later or There is always tomorrow” Literally just wasting my whole day doing nothing productive. Then its time to go to bed, I close my laptop and think about me being unsuccessful in the future due to my present behavior. Ridiculous, the fact that I am writing all this text pisses me off even more. Like I am mocking myself at this point. What type of answer am I expecting anyway, I know very well that there is no magic word to get rid of my laziness or whatever it is. I am very afraid because I know that this minimal effort will backfire VERY badly one day and I will blame my present self for messing everything up. Oh and of course I want to “be the best” lmao I am very embarrassed and disappointed in myself.