Pay Attention!!
Poker is a terribly slow game. Even online where it's twice as fast, it's slow going. Even so, you still have to pay attention or you'll never improve, it's that simple.

Pay attention to the cards. Watch how hands play out.

Pay attention to the players. Remember (or if you're online, take notes) what they raise preFlop with, what they bet with (middle pair?). Remember what they call with (gutshot straight draw?). Remember what they re-raise with (non-nut flush? or only the nuts?)

Poker is a combination of knowing the cards, and knowing the players. Every poker decision is "situationally dependant". That's why the answer to almost every poker question is "It depends".

What do you do with Aces pre-flop? It depends. On your position at the table, on the type of players you're playing against, but there's never a straight answer that covers all situations.

In the end, you'll be hard pressed to turn into a winning player if you can't be bothered to keep an eye on the game.

As Mike Caro says, It's Poker, not chess. A lot of your opponents at lower limits will be playing "outside the lines", making the conservative approach to the game less profitable. You cannot rely on them making educated decisions, and that makes a difference in your play as well.

But, as you move up in limits, or find tighter tables, the advice on this site becomes more accurate. And, until you figure out which opponents are loose cannons, playing conservative will keep the chips in your stack.