My Own Worst Critic.
I am, in fact, the above. Contrary to popular belief - this is not all negative. But I will focus on that first (to get it out of the way).
The reason why being one's own worst critic can be a bad thing is because it often tends to overexaggerate things. I tend to make many stupid mistakes in my life, and most of the time I am fully aware of them (so there's no hiding my either blatant disregard for good, or my horrible feelings about my actions). Having that nagging voice letting me know how dispicable I am...it makes things difficult. Guilt, sorrow, shame - they all tend to hang around a lot longer than they should when you let yourself become the person who tears you down.
But the criticism can be good. It allows you to remain accountable to yourself. You are able to judge your actions and understand not only their quality, but the consequences they bear. Sorrow and guilt are not bad things when they are managed and used correctly - they help to shape and guide decisions and actions in the correct direction. Testing everything by a specific criteria can help each person remain personally responsible for their own undertakings.
To understand this as a whole, however - we must understand it (at least from my own personal perspective) in relation to my faith. I am a Christian. I believe not only in Jesus (meaning He did exist) but I also believe what He said (meaning I believe He was the Son of God, I believe that He came to die for sinners that they might be set free to a new, better life). Because of this, there is a certain "blueprint" for my life. Namely, I am to do everything to strive to be made into the image of Christ Himself. If/when I look/act/think/am like Jesus - the journey is complete.
And so everyone knows now, it is a LONG journey that I am FAR from perfecting.
So how does this relate to the idea of personal criticism? In this life, because of my faith and beliefs, I am able to fully utilize the criticism to keep me accountable to the choice(s) I have made (the choice of the life I want to live and how to accomplish that perfectly). Better still, I am free from the condemnation and general displeasure that comes from personal condemnation from overexaggeration with the negative side of criticism. I do NOT have to listen to the voice that calls me evil and continuously slams my foibles. What I can do is understand that I am a precious work in progress (and indeed we all are who are in Christ). The limitless patience, love, and power of God is on my side - as hopeless as sometimes it may look.
So we must rejoice in our weaknesses and failures because they keep us humble, they keep us in an understanding of the sweetness of grace and love, and they can keep us on the right track to our desired destination. They are a means to an end. What could be a weapon has made us (and can make us) more than conquerors.
To all who believe - use these things to your advantage.