If you had nothing to do today.... what would you do? If all of your assigned tasks magically disappeared, or if you couldn't get to your source tree/test system/primary work environment.... what would you do?
Give yourself 30 seconds to think about it.
This is your subconscious talking to you. If you can't come up with anything, then that's a sign that you're either in the most focused job ever, or you're bored and kind of disengaged. After all, there's the stuff you're supposed to do, sure. Those are external requirements and needs - things that "management" has decided is important.
There are also your internal requirements and needs and ideas. These are the things that don't make it onto the backlog, or that you haven't told anyone about because they're not really bothering anybody else. Those are the things you would do if you didn't have any external requirement or needs. And if there's nothing - nothing at all - that you want to do better, no itch you want to scratch, no idea you want to try out, then you are in a big rut.
The external requirements are the world talking to you about this thing you're doing. The internal requirements are the whispers that say, "I care about this thing I'm doing." They're the things that turn you from hands on the keyboard to an engaged team member. And an engaged team member is almost always a happier team member.
So get engaged. And if you're not, then if you had nothing to do today..... you should find something interesting, either where you are now or on another project.