There is this crazy swimmer here - he swam down 50 miles of the ganges river in some iron man contests - and he constantly swims between islands.
The way he visualizes is splitting down the goals to smaller portions. "I only think about the next 15 minutes, if I would think about the whole thing I would go crazy.".
I've found that's the best for any sort of physical task - for running it was "ok, I'll run to that light post" - a run could be an hour and a half of light posts. And for strength training it's always a lie on the bad days. "I'm not feeling great so I'll only do three sets today." - I always end up doing my prescribed five, but the size of the lies change as I need it to.
The way he visualizes is splitting down the goals to smaller portions. "I only think about the next 15 minutes, if I would think about the whole thing I would go crazy.".