it can be hard sometimes if the person isn't motivated too (very hard), I know depression and low mood play a big part in it
as for smelling bad- well, some people might not be aware of it so don't do anything about it, and their's also conditions that make you smell bad- okay I can think of one, only one, but I knew someone with it and believe me it isn't pleasant- when I was around her, I tried to just get on with it.. like she was anyone else