Re: folding a hand preflop after it is raised
 

A theoretical point:

If you limp in, you are basically saying that you think your hand is going to win enough to merit investing 1 SB into an X SB pot. If it's raised behind you, you'll usually have to decide whether it's worth it to invest 1 more SB in a pot that is now usually 2X SB or better.

Sure, some things have changed; the raiser probably has a good and and so on, but that information is rarely enough to suggest your is not even worth half of what you thought it was worth when you first limped in.

So that's why when you call 1 pre-flop and it's raised behind you, it is basically always correct to call 1 more. (If it's two back to you, you can consider folding).