The last time I had a 1 on 1 with David, I was challenged to try visualising a hard set before going to training for that set. I did this for our Saturday training, which usually consists of 6x50 all out from a dive, suited, with 350 metres easy swim right after (start interval 7 minutes). I usually do all six fly. When visualising, I put strong emphasis on the dive, the underwater kicks, the breakouts, the turns, the breathing pattern and the finish. The visualisation made it easier to better time my turns and finishes, resulting in faster times. It was also easier to work through the last 2 reps, where I usually get lactic acid because I had already simulated that pain in my head.