For me it is sometimes "excited to do stuff" but it also is often "life got in the way and I never got a chance to unwind."
I really need to unwind before bed, and if I don't get that time to turn off my brain, I'll be up all night. So I stay up late until I feel ready for bed, but I'm screwed either way at that point.
Yeah seems like I'm still on the good boat where I'm not actually forced to be concentrated on something all the time, I just do it because I'm like that, and have free time to focus and obsess over the stuff that I like.
Getting life in your way often seems to be way worse.
I really need to unwind before bed, and if I don't get that time to turn off my brain, I'll be up all night. So I stay up late until I feel ready for bed, but I'm screwed either way at that point.