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Well, from your post , one thing is quite evident , that you have been ruminating over past events of your life , and the more you dwell on them , the more you realize what went wrong and then you start blaming yourself for what happened , and how you could have avoided a lot of pain to others , and thinking about all this ,makes you feel worthless and self critical .
Self worthlessness is a strong indicator towards the fact that you are suffering from Depression , which has stemmed from your thoughts of events of past , which you feel could have been better , if you had done something differently. Well, i can tell you that in life what happens that is ought to happen , after all that is destiny , so what has passed has passed and athough mind being a very sensitive organ makes us feel guilty of past events , which we all the way knew that we could have done better to prevent the unfortunate events , but it was not meant to be that way , so i would suggest rather than dwelling on your past , and loathing yourself , for things which could have happened differently , it is better you concentrate on your present , which actually will make your future wonderful and blessed. All of us in our lives feel that things could have been different today if we had acted this way or that way , but , by thinking too much on this , we waist our present to cherish good things God has given us in life and we often forget to celebrate our lives.
So, since you seem to be suffering from Depression , i would suggest you consult a Clinical psychologist , and get started on Psychotherapy , that is counseling in lay terms . The best psychotherapy for depression is Cognitive Behavioural therapy ( CBT) , which is a short term therapy , but has been proven to be as effective as Anti depressant drugs . As of now , i would only suggest counseling to you , and if CBT does not prove to be as useful as we expect it to be , then you shall get started on Anti depressants , some good effective anti depressants are --Venlafaxine(effexor) , paroxetine(paxil) , fluoxetine (prozac), sertraline(zoloft), Milnacipran , although i feel CBT will suit you just fine and get you out of your feeling of worthlessness and depressed mood.
I wish you best of health. God bless.
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