If you believe you can make a living as a writer, you already have enough ego.
If you have other things in your life - family, friends, good productive day work - then these can interact with your writing and the sum will be all the richer.
Beware of self-indulgence. The romance surrounding the writing profession carries several myths: that one must suffer in order to be creative; that one must be cantankerous and objectionable in order to be bright; that ego is paramount over skill; that one can rise to a level from which one can tell the reader to go to hell. These myths, if believed, can ruin you. If you believe you can make a living as a writer, you already have enough ego.