When I swim in a 50 meter pool I count every 100 meters. Sometimes I count my strokes and add it to the time it takes to swim a length to find my golf score. I am working on bringing down my average of 120 to 100. I only swim freestyle non stop to accomplish an amount of distance. While swimming after a 10 minute warm-up I'll alternate fast and easy laps followed with a 10 minute cool down. When I swim in open water time becomes my focus rather than distance.
When I bike outdoors I ride for distance and figure my average speed. When biking on the trainer I'll spin usually for 1 hour.
When I run a 6 mile tempo track workout for some reason I find it easier to count down the laps rather than the miles.
In my recent 10 mile race during the last 3 miles I used time as the countdown to the finish rather than how many miles left. I thought it was easier to say to myself, "18 minutes left you can hold this pace.... 12 minutes left and feeling strong... 6 minutes and it'll be over". This was my secret when my mind began to wander and the fatigue setting in causing me to slow down. I was happy in using this method to help me focus on the finish.
On my long runs on the road I'll use blocks of miles (3, 6, 9, 12, and 15) to help pass the miles away. On the treadmill I'll use blocks of time (15, 30, 45, 90 minutes) to help pass the time away.
I find it amazing how the mind plays a numbers game to help pass the time while training and racing.