There's a bit of a Catch-22 when it comes to all this. If you truly love and accept yourself, how can you want to change yourself? Aren't these two ideas complete opposites?
I guess the shortest answer is: it depends. It matters what your desires to change are based upon. If you look in the mirror and say "I hate (insert body part)," then you aren't actually accepting yourself. If you look at a magazine and think "I wish I looked like (insert celebrity or model)," then your desire to change is not based in improving yourself.
I think that if you do really love yourself, the idea isn't so much about change, but about preserving and improving. You want to be the best version of yourself. You want to push yourself to be better, not just more fit. It's why we continue to go to school, earning bachelor's and master's degrees. It's why we sign up for marathons or Italian lessons.
The thing we absolutely don't want to be is stagnant. You'd never set about trying to compose a masterpiece when you don't know how to play the piano, right? You accept that that's not one of your skills. You accept that you're better at math than writing. You can accept all different aspects of yourself except your appearance. That doesn't make much sense!
I strongly believe that you can't succeed in change if your desire to change is based on outside forces. It has to come from within. That's why it's so hard. Think about the people that are told they have high cholesterol or blood pressure or diabetes that then go on to change their lives. They do because their health is at risk. It's no longer about aesthetics, it's about survival.
If it were easy to change because we want to look good on the beach, then we'd all have done it by now. One of the reasons it's not easy is because we haven't accepted ourselves and, therefore, our goals are all off. I'd love to have legs like Gisele, but that's not going to happen. Ever. First of all, I'm 5'5". But, does that mean I can't have fit legs? No way. I just have to accept who I am and make a decision about what fit legs means for me.
Of course, I'm always going to push myself to do more, to be more. I keep coming back to the idea of balance. I have it in so many places in my life. This is one area where it's hard for me, but I'm gaining perspective. Sometimes the harder thing is easing up.