Never think lowly of yourself, or others will think of you that way.
No one is good at everything, but we are all good at something. If you failed in a task, don’t let it get you so down that your spirit is suppressed. No one goes through life without making mistakes… and you will make more. It’s okay to feel disappointment when you blunder, but then move on.
Each of us has many good qualities, and so do you. When you feel blue, focus on the natural abilities which have been given to you. Then feel good about yourself knowing what they are.