If my aspect (Life) is something that I need to grow into and learn how to be more of, should my class also be that? If I'm incredibly selfless out of feelings of worthlessness and a lack of self esteem, should I have some kind of Active class to teach me how to be better balanced, or is growing into being a Life player enough?

Well, yes and no? Sometimes a Passive Player needs to still be Passive to be happy, but just learn to be less self-destructive/sacrificial. There’s degrees of Activeness and Passiveness, and what comes naturally should be what you should pursue. Trying to invert your Passive/Active Role forcefully could be rather toxic as well.