Your driving instructor, the barista with the AH-MAZE-ING eyes, your older brother's BFF… we've all had a few inappropriate crushes over the years.
Most of the time, they're just a bit of fun, or they might even end up progressing into something more.
But what happens if you fall hard for someone who simply doesn't feel the same, or worse, who is totally off-limits?
Unrequited love might make for a great movie plot, but when you're feeling it in real life, it can be pretty tough to bear.
If you feel like your life is being overtaken by a crush that's going nowhere, clinical psychologist Ramani Durvasula says you're not alone.
"We have all had them and will likely continue to do so all of our lives," she tells Women's Health magazine.
So what to do when that crush becomes more than just a flight of fancy? Dr. Durvasula has some tips…
1. Know that it's totally normal
Crushes aren't just for tweens who want to be Mrs. Harry Styles. Falling in love – no matter how logical it is – feels amazing, and it's something our body craves. So don't beat yourself up for falling for the wrong guy. You're not the first person with an unrequited crush, and you won't be the last.
2. Don't let yourself be strung along
If the lad you fancy is leaving you waiting hours or even days for a one-word text, despite being oh-so affectionate in person, you might need to give yourself a good talking to. "Unrequited crushes may like the attention and validation," says Dr Durvasula. "While they have no intention of doing anything about it, they may string the crusher along longer."
3. Know your own worth
Yes, relationships have their ups and downs but you should never be left feeling like you're not enough. Love "should be a gentle and reciprocal process," says Dr. Durvasula. "When we fight for it, we often lose sight of whether this is even the right person." Have a think about what you want from a relationship – are you going to get it from this person?
4. Keep your distance
At a certain point you need to accept that things simply aren't going to work between you two, and at that stage Dr. Durvasula recommends cutting contact for the sake of your own sanity. Even if you work with your crush, try unfriending or blocking them on social media, and avoid events where you know you'll see them… at least for a while.
5. Focus on meeting new people
Just because John in HR is the wrong guy for you doesn't mean you'll never meet the perfect man… but you have to be open to meeting new people. Put yourself out there, says Dr. Durvasula, and don't dismiss every new person you come across.