The idea that my spouse is better than I am and I don’t deserve him/her can, in fact, be a good attitude in a marriage. After all, if he/she is so much better than I am and I don’t deserve him/her, then that can be a great motivation towards tikkun hamiddos and other self-improvement so that you CAN grow into someone who deserves him/her. On the other side, if you feel that YOU are better, and that you spouse needs to improve, that is a recipe for problems in the marriage.
Don’t get me wrong; self-esteem is very important, and one shouldn’t take the thought above to the extreme. However, please don’t say that feeling such as yours are bad. Channeled in the right way, they can be the pathway to a great marriage.