It is highly important to tell your children you love them. Its all about making them feel confident and gives them a positive outlook about themselves. Praising them as often as possible is also a good booster for them. Whenever they do something cool, give it credence so they want to do more coolness.

Even when they do something not so cool, rather than call them a bad person, just point out that you didn't like that particular action, so they continue to know you love them, but not necessarily that behaviour they may have displayed.

I too have three boys...I love them and do they know it!