Should I re-take the GMAT?

I don't see the downside to taking it again except for $250 and a few wasted hours studying. But, you're 22 and probably no family. What else are you going to do in your evenings? If you are worried about doing worse, I think the question Adcoms would have when reviewing your score report is..."So he bumped his score up 100 points in 2 months, I wonder why he didn't try taking it one more time." The Adcoms I have talked to through my application process continually stressed that you shouldn't leave gaps in your story that they have to fill in on their own, because they all have pretty creative imaginations. If you take it 1 more time and get a 670, it will be clear that 680 is your number. If you don't take it one more time they could ask the question, "Did he think 680 was good enough for our school, or was he lazy, or was that just the best he could do?" If you are worried about bombing the next GMAT, don't send the score report to any schools. That way they will only have your 2nd score on record if you did send that one.

In my case, I took the test 3 times and my score stayed in a 20 point range. I knew my score was my number, I owned it and I accepted it. There were no what if's going forward.