As @dpworkin suggests, if you can find a way to make yourself look much larger (or much smaller, if you can manage that), then even if your face seems familiar, the rest of you won’t, and they’ll tend to discount the facial resemblance.
You really want to disguise your gait, too, though, so crutches, a cane (practice) or a wheelchair could help a lot. (The wheelchair also allows you to cover your legs with a blanket, for example, which aids in hiding parts of you.)
If you can dress very formally… or in rags… and your friend isn’t familiar with you in this getup, then “you” won’t fit in your friend’s recollection of “how you dress”.
Dirt, scars, bandages, a limp are among many more suggestions.
All I’d have to do is wear a fucking New York Yankees baseball hat and no one who knows me would recognize me at all.