Use a small Bag

i find that the larger a bag is, the less likely i am to pick it up and take it with me everywhere i go.
for this reason, i get the smallest camera bag that can hold the equipment i don't want to be without, and keep my camera, lenses and assorted "go anywhere" junk in that one bag.

the bag i use is the lowpro slingshot 100

i can't help but notice how much it's gone down in price since i bought mine, so i'm guessing that it's popular.

i could use a larger bag which would hold all my lenses, all my gadgets, and has room to strap my tripod on the outside, but i would never use it. then i would never have my camera with me, and i would never be able to take the shot.