Measuring progress

I am having great fun this week with the focus switching to turbo training on the bike.  Short, sharp focused sessions with lots of key points to measure my progress.  It certainly does help the time pass and motivates me to work hard.  But tonight I was swimming and forgot my garmin so I had nothing to measure against.  I think I swam well but without measurements I can't tell so I won't make that mistake that again.
The gym and core sessions are also having an effect as I felt stronger in the water and kept my form which improves my swimming - unfortunately though I couldn't measure the progress.  The gym and core workouts aren't as much fun as the other sessions but the results are showing so that will keep me going.
It's small incremental improvements that will make the difference come Lanza Ironman in May so I must make sure I don't slack off with the training.