21 isn't that hard, especially with the hint now.
I learned a lot from my then zebulun journey (Cyberarmy's challenges) because I persevered. I was a complete noob then. I remember I was stucked at the Blackjack level for quite a while, becaue I didn't know what to do. I read the forum for that level several times - nobody gave a hint because you were not supposed to. But through what people wrote after they passed the challenge, I got an idea and eventually made it.
That whole experience enriched my knowledge of Internet security, CGI and Javascript. I'm thankful for it.
So it depends. If I were here just for fun, then I would probably give up as soon as I am stuck. But if I think there's something to be gained besides the fun, then I am likely to persist.