My parents esp my mum doesn't like my boyfriend,cause she feels that he is too short for me. wat to do?

I am 24 this year, and he is 31. If things go well, we hope to get married the end of next year. We have been together for 8 months now. Since when i was young, i have always been the daughter that listens to them regarding everything, and now they are trying to control who i want to be with as well... I know that my parents want me to find the best person, but how can i make them understand that i kow what is best for myself, and stop them from pressuring me on what i should do, cause this is really making me very upset, and creating problems for me and my boyfriend. Can anyone help?