Over expectations and overconfidence I have caught myself many times saying to others that I will do this and that. I also tend to confirm that I can and will do things, when I'm asked about it, even when I am not sure. Often people end up criticizing me when I fail to achieve what I promised to. 

I also have a lot of over-expectations about myself. I intend to learn so many things or read so many things or meditate a lot etc., and also I always get carried away buying things just for the sake of fulfillment. I want to over achieve. 

My meditations have helped me realize that this was due to my obsession with wanting to be 'great'. I want to always be appreciated and want to always feel high. How can I resolve this problem of mine?
You are not alone on this… @Ashwin Kumar. You have good company. When you stop and think about it, that’s what a lot of people do in this world. They do something because they think it makes them better than other people. That whole mindset—the idea of wanting to be better than others or that they are worse than others or equal to others—is a real trap because it tends to swing you back and forth between extremes: either exaggerated self-esteem or exaggerated self-hatred, back and forth, back and forth. And either extreme can make you miserable because the idea of self, of who you are, becomes the big issue in life. You have to do everything you can to shore it up. Then when you find yourself doing things that are not up to that high standard, you feel like a failure. It’s good to remind yourself that all those issues are useless. They don’t accomplish anything at all. We are practicing this Dhamma to overcome conceit, but conceit has its uses.

So as long as there’s going to be conceit in your mind—i.e., the idea that you define yourself in a certain way and you define yourself against other people in a certain way—try to use standards that are wise. Look in terms generosity, virtue, conviction, discernment. At the very least be your own best friend in terms of your values and try to keep those values clear and articulate so that you notice when you’re deviating from them. So that even though we’re living here in a land of wrong views, you try to create an island of right views around yourself.

When you can let go of that conceit of over expectations and over-confidence—even though you can’t totally conquer it, at least put it out of your mind for the time being—it allows you to look at situations less in terms of what you are, and more in terms of what you can do with the range of skills at hand.