Basically, anything that distracts and/or engages/focuses the mind; the more intense the concentration/focus, the more distracting from pain (and other symptoms, for that matter). Interactive activities/distractions work better than passive ones, and those that elicit joy/enjoyment/satisfaction (e.g. creative outlets) work best of all.

It's been argued that keeping the mind distracted/focused/occupied doesn't actually reduce pain, but keeps one from thinking about it/dwelling on it. I say, what difference does it make? If it works, it works.

Doc