I'll give it a shot.

In poker you want to put more money in the pot with strong hands, and less money with weaker ones. However, your hand is secret information, and raising too much "polarizes your range," giving your opponents the opportunity to outplay you. Finally, hands aren't guaranteed -- good hands can lose, and bad hands can win. So you need to bet big, but not too big, with your good hands.

So my buddy and I sit down at the table, and I get dealt a few strong hands in a row, but I raise too big with them -- I'm overconfident -- so I win a couple of small pots, and lose a big one. My buddy whispers to me, "dude...you're overplaying your hands..." Ten minutes later I get dealt another good hand, and I consider his advice, but now I bet too small, underconfident, and miss out on value.

Replace the conversation with an internal monologue, and this is something you see all the time at the poker table. Once bitten, twice shy and all that.