If you don't accept yourself, you won't live fully, and if you don't live fully you'll need to get full some other way.
Happiness comes from accepting the present situation, whether it is something you wish to savor as long as possible or change as quickly as you can. Neither is possible without acceptance as the starting point, because without acceptance you are living on the periphery of your life. There at the edges, you can't fully enjoy the good stuff or do anything about the rest.
Life has its rhythm and we have ours. They're designed to coexist in harmony, so that when we do what is ours to do and otherwise let life be, we garner acceptance and serenity.