University student who chronically does nothing about assignments, tasks, or even handing in time off sheets to work because "I don't need to do it nooooow", how did people in similar situations get themselves disciplined?

For example, if I get an assignment that's due in 3 weeks, for the first week I'll completely not think about it because there's no chance that I would need the whole time to do it, then for the second week I'll take my stuff out and sit down at the computer a couple times and do barely any work until I think "I know what I'm doing and feel confident about this assignment, so I have so much time". then for the last week I'll be in a constant state of knowing I should be working and not truly being able to relax cause it's in the back of my mind, but still hardly doing anything about it because I know that I know how to do it so I don't feel like it's an issue, then after days of sitting at my computer with the tab open but also with Youtube open, I'll have no issue spending hours in a row doing homework unbothered in a rush to do it because I finally feel like I actually need to do it. I'm pretty smart I feel like, so It's worked good enough, but it's not sustainable at all... until summer comes around and all there is is work and chilling and I feel like I'm all good and the whole cycle repeats.

I try and analyze myself and I find myself having a similar mindset pretty much everywhere else where I feel like I'm super confident in my ability so I just do not feel a need to do things.

Like right now I have an overdue assignment and a couple big ones coming up and physically I have absolutely not enough for any of them, because I'm still doing good in the classes and my prof told me to hand it in when I can and it's all good, I feel pretty much no pressure to do it right now. Or like I do feel pressure, but I'm telling myself "I know exactly what to do, so what can one more funny episode of IASIP do?"