Subject it to as much opposing evidence and logic as possible.
Madness string 81326
Insecurity is pointless. It is beyond arbitrary and is actually a weakness. Be aware of your flaws, but embrace them. If you can change them, then change them. If not, then accept them as a reality and move on.
Why? Excellent question. You should always ask that question, even if you think you already know the answer. You will find that a great many things are far deeper than they appear.