Our culture today is obsessively focused on unrealistically positive expectations, such as being happier, healthier, smarter, faster, richer, sexier, etc. This type of mindset is further propagated by the media, who try to sell being extraordinary. However, they are lying - you are probably just average. If you buy into their manner of thinking, you may begin to feel inadequate.
If you keep looking for the bigger and the better, you will become overly attached to the superficial and fake, and will spend the rest of your life searching for the happiness and satisfaction that is not there. When you accept yourself (including all your flaws!) you will achieve true happiness.
Accepting yourself also means to understand that you will make mistakes, but that shouldn’t keep you from trying again. You may not be the best in a certain field, but if you try, you may still be able to do well in that field.
Accept yourself - averageness and all.
Your flaws do not make you any less of a person. Yes, they make you different, but there is nothing wrong with being different! Accept your insecurities, and you will realize that you are more confident and charismatic. You are who you are, and accepting it is the first step towards achieving happiness.