If you can't get in the zone, do something else.
If you're not giving your all, take a break.
It's better to either completely work hard or completely have fun.
Barely working, sucks. So does barely having fun.
Anything in between will probably drive you crazy after a while. Listen to your intuition, and if you're not trying your best, take a 15-20 minute break to do something different. Be honest with yourself, because whatever work you're doing deserves your full attention.
The same goes when you're having fun too. You deserve to have awesome fun when you get the chance or when you feel it's necessary.
We can't pay full attention to two things at once. That's just not how our brains are wired, and multitasking usually isn't the most effective technique for that reason. The minute you feel distracted, go for a walk around the block to get your energy back. Listen to that song that’s stuck in your head so it can finally go away. But then get right back into it with full force.
You don't want to be overcome by distractions, but you also don't want to half-ass a project just because you tried to blast through it. Learn to recognize which distractions will linger in the back of your mind involuntarily versus the ones you create on your own. You can prevent the second kind, but the first kind will chip away at your mind if you don't do something about it.
There's nothing wrong with taking quick breaks, in fact, it's an investment that you might not be taking enough.