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?