The general decision making scheme is as follows:
1. You see the potential of your cards, their strength or weakness.
2. You see the possibilities to improve your hands during the game.
3. You make the final decision based on card odds and pot odds. If the ratio is favourable for you, you call. If it is not, you have to fold.
In order to get a long-term profit you have to follow these rules but that does not mean you have to do it always. On the contrary, otherwise, your opponents will reveal your scheme of playing and your plans. When you are using the general rules, your profit is going to be less than if your play is more flexible.