Learn and Think, Don't Follow Rules!
Many people who are just getting started with poker seem to want to get all kinds of strategy sheets and books to tell them what to do in every situation. Following strict guidelines like this rather than thinking for yourself if a big mistake. Unlike blackjack there is not always a correct strategy to follow in every situation.
Advice and tips sheets can not take the place of your own good judgement skills. You can't depend on pre-planned strategies if you want to be successful. Players who do this are doomed to failure as they will be very predictable and won't always take all variables into consideration when making decisions. The best poker players know the basics and make their decisions on the fly and play differently as the situation requires.
Judgement skills cannot be taught, but they can be learned by lots of practice. Learn from your mistakes and try to figure out what you should have done differently each time things go wrong. Do you make the right decision more often than the wrong one?
Looking at the hand history in online poker can help you learn the right decisions. Most poker rooms will display all the losing hands in this history even if it is not shown on the screen at the showdown. If someone calls you on the river and you still win, check the hand history and see what cards he had. This will help you learn if you are judging your opponents correctly.
To play poker you have to have confidence in yourself but you also have to think for yourself. Don't get bent out of shape over poker textbook guidelines, you are the best judge of the current situation and not some book written perhaps years ago. Good poker knowledge and a basic familiarity with the guidelines combined with situational judgment skills is what makes a good poker player. Losers don't think for themselves or perhaps just don't think at all!