"tryhard"

Honestly, if someone else is doing better than you in something, whether it's academics or sports or whatever, what's the use of calling them a "tryhard" or an "overachiever"? (actually I have less of a problem with 'overachiever' it's more of a joking/friendly term, but still)

Once, I was talking with my friend about some girl that her brother used to have a 'thing' with and she told me that she disliked her. Since I knew this girl was rather well-liked and popular-ish at our school, I asked her why. She couldn't answer me directly, and finally said "...she's a tryhard."

...Okay.

I don't know if I have this correct, but to my knowledge, 'tryhard' means exactly what it sounds like: people that try hard. 

Is that a bad thing?

Is it bad that people try hard to do whatever they're doing that's better than whatever you're doing? Or are you just jealous?

"Oh, yeah, I didn't try that hard, so ofc so and so beat me in blah blah blah, yeah, they're just a tryhard."

Really.

Another instance: yesterday, at time trials during swim practice, my friend was talking to some other people about 'tryhards', something along the extent of "wow these people are trying so hard, wearing race suits/caps blah blah tryhards"

So, when they beat your ass at swimming, it's because they were wearing race suits and you weren't? Or was it bc they're just faster than you? Oh no, you have to explain the speed difference away with "they were trying hard" and you weren't.

...Since when has trying hard become a bad thing?