Personally, I find that a change in my appearance goes a long way toward encouraging me to change my self-image, even if I only make a small change.

For example, I may spend some extra time "prettying myself up", whether that be a new haircut, a different style of clothing, what have you. When I find I like it, and I like how I feel like that, I make an effort to upkeep that appearance, and eventually find that even on days when I lapse and bum around, I still feel like I look good, simply because I've put effort into myself in the past, and because I think everyone deserves an "off" day.

...Does that make sense?