Sometimes life throws you curveballs. Sometimes they're good, other times they suck. No matter what, you're the most important aspect of your life. If that curveball is the passing of a family member or close friend or a sudden bout of depression, taking care of yourself is more important than school.
"But school is always more important." Actually, it's not. That was the mindset in high school, but it really shouldn't be. If you physically cannot bring yourself to prepare for classes (and I don't mean procrastinating -- these are two different things), then maybe you should take a little break. A break can range anywhere from a "sick" day to an entire semester. The only person who gets to decide that is you.
No one's saying to drop out of school, unless that's absolutely what you need at the moment. Other times, taking an incomplete for a course works too. You have time to mourn the loss of a loved one or find the right medicine to help a chemical imbalance in your brain. Yeah, you'll have to eventually turn in your work, but an extension doesn't hurt anyone.
And yeah, you probably don't want to be doing this every semester... only when it's absolutely necessary. But there isn't a letter in the whole alphabet that is more important than U (pun fully intended). If you need a break, for whatever reason, just talk to your professor. Explain the situation and why you need an incomplete. The worst thing that could happen is they say "no."
"What if they do say no?" Well, it's time for a little radical acceptance. According to Psychology Today, radical acceptance means "completely and totally accepting something from the depths of your soul, with your heart and your mind. You stop fighting reality. When you stop fighting you suffer less." Obviously, it's a psychological term, but it truly does wonders.
You can also use radical acceptance when life throws you that curveball. You can say to yourself, "God, this sucks. But I'm going to make the most out of this crappy situation and find a way to work through this." Sometimes you can't always find the light at the end of the tunnel. You need to take the time.
That is OK.
You are no less of a student if you take an incomplete. You are no less motivated than the student who manages to work through tough situations. You are the only person who knows what is best for you. If that means taking an incomplete or toughing out a shitty situation, then you do whichever you need. Your mental health is more important than anything -- if your brain doesn't work, nothing else will either.