Against the following range 66+, AT+, A6s+, KJ+, K9s+, QTs+, J9s+, and 98s your jacks have a 62.8% chance. That's a nice hand.
Look what happens to your chances against this range when certain flops come.....
First, rainbow flops with overcards, few draws. Only one suit matches one of the Jacks.
Q72 : 61.9% chance.
K72 : 57.5% chance.
KQ2 : 52.6% chance
A72 : 47.6% chance.
AK2 : 37.2% chance.
Second, wet flops with more draws. The jacks are JsJd.
QcTc6h: 52.4% chance.
KcTc6h: 48.9% chance.
KcQcTh: 47.1% chance
AcTc6h: 40.5% chance.
AcKcTh: 32.6% chance.
As you can see, you shouldn't just give up when you see overcards. Especially when it's a K or Q, and the flop is dry you still have pretty good chance. Try to get to a cheap showdown. If villain is passive and he bets you're probably beat. But if he's a aggressive and likes to
bluff maybe call one or two bets.