One of the biggest mistakes players make, is not knowing when to laydown a big hand. There are always going to be times when the cards you are holding, no matter how good, are going to get beaten when the board gets dangerous.
There are players who simply refuse to let go of their hands, even when the board cards are giving off danger signs, they will just be concentrating about playing their own cards instead of looking at the hand as a whole. Say if you are holding Ad-Ah and the board is Ks-Qc-Qs-Js-9s, and there is betting and raising on the river, then it should be obvious your Aces are not the best hand.
Given the above example, there are four probable hands that will beat your Aces;
Two Pairs, players will always want to see the flop with two high cards, thus making two pairs
A Set, players holding a pair of K, J, or a 9’s will make set, or one Q will have you beat
Straight, a player holding a 10 will make the K high straight
A Flush, Any player with a spade will make a flush.
Against one opponent in this situation, unless you have some sort of read on their betting patterns, it is probably always best to fold. Against more than one player folding is your only real option. With experience, making big laydown decisions will become easier, and you will get to recognize other, less obvious situations that will call for you to lay down your hand.
It is not always so easy to make laydowns online as you have to rely on betting patterns and playing styles to get reads on your players, who will come and go more quickly than in a “live” poker room. But if you are aware of all the cards in front of you not just your own, you can get yourself out from some difficult situations, and save yourself from losing more money at the tables.