Daeboo, one more thing.... just do what you CAN and don't feel bad about what you can't. I have always been very athletic and competitive so it was soooo hard for me when I got a thyroid tumor and not only gained to my highest weight ever but was a slug from the hypothyroid (which praise God is apparently okay now with med adjustments). But when I first started forcing myself to walk again I had to stop and lean on every lamp post, sit on all the rocks, hang on the fences, etc. LOL... plus I have plantar fascitis and bone spurs, AND a weak knee. A bit of a mess LOL. But if I needed to lean on a pole I did.
And guess what... after a while I began bypassing some of the poles... now I only stop to rest for a moment or so on really long walks! It DOES get easier. But LOL still... there are times when I am lugging my big ole butt up a big old hill (which if you live in Seattle might as well plan on) and here will come some young guy or chick jogging along past me LOL. Oh well....
Also when I feel I cannot put another foot in front of me I picture all the little fat granules and calories bursting out into the air around me in all kinds of pretty colors LOL... or I start thinking about my cyberpals at 3FC and start praying for each one of them as their name and situation comes to mind! It WORKS!
Oh and if you don't have a pedometer I highly recommend getting one! Amazon.com sells the Omron HJ-112 which seems to be the favorite around here; I just ordered one myself as the ones I had kept breaking. It is fun and helps you see your progress.