When you think that you had alot of trouble or problem, think of those who are worst than you. Those being physically handicapped/impaired, those living in the 3rd World Country and had no time to worry about anything else other then to worry for their next meal.
Problems gone.
When you lack of confidence for something, look at the bigger picture. The result will eventually be worst when you are lack of confidence. It finally make sense that actually theres nothing to fear. It cant't get any better without confidence.
Gain confidence.
Do kind deeds everyday and try to help if you can. Stop counting on "I did this today" and expecting something in return. No expectation, No disappointment. Don't be calculative, You eventually get nothing out of it and at most you get yourself tired mentally.
Be helpful.
Don't always compare to those people who are better than you, compare those who are worst. It makes your life more easier and helps you to understand, you still live in a freaking good life. So stop complaining and whining about your life.
Being satisfy with what you have gotten.
Satisfying is the key word to happiness.