Beginning players often have increased attachment to hands they've already invested chips in. Often, they'll engage in rhetoric along the lines of oh well, I already put 200 chips in, so I might as well put 200 more in. If you think of your poker decisions along these lines, you're probably not a winning player. A key concept in poker is that money you've put into a pot is no longer yours. You can't have any attachment to it.
One place where this mentality kills players is defending the blinds. Some players feel like it's their duty to prevent aggressive foes from stealing their blinds. Aggressively defending blinds can be problematic because it leads to playing inferior holdings out of position.
No-limit hold'em is a game of position. Players with position have an advantage over players without it. Fortunately, it's also a cyclic game, meaning that players get to take turns when it comes to enjoying the advantage of position.
There's a certain "right" of position that exists in no-limit hold'em. When you don't have position, you need to yield the right of way to your opponents who have position. You make your money in no-limit hold'em by taking advantage of foes who don't yield the right of position to you when you have it.
Of course, this doesn't mean that you should never play hands when you're in the blinds. If there's a small raise and a bunch of callers, and you have a small pocket pair or a suited connector in the big blind, go ahead and see a flop. However, this call isn't to defend the blinds. Instead, it's because of the great pot odds you're getting with your drawing hand. A more direct blind defense situation is when you have a hand like A6 in the big blind, you have a stack of about 8 or 9 big blinds, and a very aggressive blind stealer raises from the button to 3 big blinds. In this case, you can play your hand by shoving all-in. When you're short stacked, your positional disadvantage disappears because after pushing all-in, there's no action on future betting rounds.
Simple rules of thumb are sometimes tough, but as a starting guide, only play hands out of the blinds when one of the following conditions is met:
1.) You have a premium hand
2.) You have a drawing hand, and you're getting great pot odds
3.) You're short stacked, and you have a hand that's ahead of the preflop raiser's range. Meaning that you can simply shove all-in with what's currently the best hand.
Other than these three cases, you don't defend your blinds by playing hands when you're a blind. Instead, you defend your blinds by proactively stealing blinds when you have position.
