Agreed with others. I once placed my iPhone in a way I can see the timing, and I imminently realized how distracting it is.
Record your times, but in a way that you can't see them during your session. The reason why I say record your times is to have a general idea about your progress.
2011 MINI Cooper S
previous cars: E92 M3, Z4MC, Z4 Roadster, E36 328 Sedan