My t says there is no such thing as multi-tasking. The brain only handles one thought at a time (albeit perhaps in fractions of seconds). When I'm having trouble with flashbacks, he tells me to DO something physical or use my brain VERY actively for something like doing puzzles (reading doesn't work; we tend to zone out). If you're swimming laps in the pool, your brain will stay pretty focused on swimming. Walking while listening to music is a good distractor.