Once a wise man drew a line on a board and told his student to make the line shorter without touching or erasing it. How would you do it? You have to shorten a line without touching it. The intelligent student then drew a much longer line underneath that line. So, the line automatically became shorter.
The lesson here is that if your difficulties appear to be very big, lift your eyes because you are only focused on yourself. If you lift your eyes up and look at those who are in a worse condition than you, you will suddenly feel that your burden is not as bad as you thought it was. If you think you have some big problem, look at people who have a greater problem. Suddenly, you will get a confidence that my problem is much smaller, and I can manage it.
So, the first point on how to be happy is to see the world where there are greater and bigger problems. Then, your problems will appear smaller. The moment your problems appear smaller, you will get the energy and confidence to deal with it or solve it. In simple words, serve those who are in greater need.
Second, look at your own life. In the past, you had many problems. They have all come and gone. Know that even this will go and you do have the energy and power to overcome it. You will get self-confidence by understanding and looking at your own past.