I want you to look in the mirror today. Really look. This is the body your Heavenly Father gave you. It isn't perfect, and maybe you don't like different parts for various reasons, but it's the body that you have been given. No person or body is perfect, despite what we see in the media, or what we think when we look at other people. More than likely you're doing your best to take care of your body. Your best is NOT going to look like someone else's best. EVER. And that's okay! Is there something you could change or do better? Of course there is, that's life. But there is no need to beat yourself up about not being perfect or even close to it.
Not all of us were built to run marathons or climb mountains. Maybe you have health problems (like me) and can’t hardly get out of bed, or go get your mail, let alone taking a shower or cooking most days! There is a reason that our Heavenly Father has counseled us to not run faster or labor more than we have strength. Everyone is in a different place in their lives, with different abilities and health levels.
If our bodies were intended to remain perfect throughout life, then skin issues, stretch marks, cellulite and wrinkles and other health problems wouldn't exist! We would all have similar experiences because none of us would be very different from each other, and so we wouldn't learn some of life's greatest lessons: self acceptance, appreciation, tolerance, and gratitude. It is important for us all to develop an attitude of gratitude for the blessings of having a body and a life to live, even if with your current body and circumstances don’t allow you to do in life the same things others can do.
In conclusion, what I want to be taken to heart from this is that when you do your best, it is YOUR best. Not someone else's best, so stop comparing yourself to others! You aren't doing yourself any favors, even if you compare yourself to others under the guise of self improvement. A lot of us would be much happier if we stopped measuring ourselves with someone else's ruler and just accepted ourselves as we are.