Let people earn your trust. Remember that things are not always what they seem. Learn to look behind the obvious. Play is one of the most important things in life. Play hard and freely, and don't stop when you're an adult.
Work is important too.
Discover ways to find pleasure in your work. When problems seem too hard, work on them a little at a time. Learn to sacrifice, for others, and on behalf of your own future. When you're disappointed, try to look at the big picture. Some day your present problems won't seem so big.