Three years of studying, can't break a 600.

First of all, most (more than 50%) of test-takers don't score above 600, and those test-takers are already a smart bunch. So, there are worse things than not breaking 600.

Whether or not use stop pursuing your target score is your choice entirely. I guess an important questions is, "How important is it to you?"

I should also point out that there are several MBA programs out there that accept GMAT scores much lower than 600, and there are many that don't even have a GMAT requirement.

I hope that helps.

Cheers,
Brent

Then keep at it.
For inspiration, you might want to read a few threads in the "I Just Beat the GMAT" forum. They were posted by students who achieved significant score increases:
- https://www.beatthegmat.com/8-attempts-l ... 20618.html
- https://www.beatthegmat.com/480-550-620- ... 05009.html
- https://www.beatthegmat.com/from-490-670 ... 23860.html

Cheers,
Brent