If you can't fly, run. If you can't run, walk. If you can't walk, crawl, but by all means keep moving. Dr. Martin Luther King Jr.

*If you can't fly, run. If you can't run, walk. If you can't walk, crawl, but by all means keep moving.

To me, this quote means you should try your hardest at all times. I also think it means that you should not give up. If you cannot fly, don't quit, try running. Even if you cannot run, still don't quit; try walking. Even if you cannot walk, then try crawling, but whatever you do, do not give up!
I think this is a great quote! It can be used as a very good motivator to keep people moving along in the right direction. For instance, if you cannot lift 100 pounds, then try 90 or 80 or 70. Try something, do not give up!
I believe this quote is telling us that we will not always be able to go all the way, which is okay. All you have to do is try your best and give 100 percent. We cannot always go all the way, but our best, is all the way as long as you try!