The best time to practice mental rehearsal is at night in bed, just before you fall asleep. The last thing you do before you doze off is to imagine yourself performing at your best the following day. You will be amazed at how often the upcoming event or experience happens exactly as you imagined it.
A relative of mine. . . spends his time producing improved breeds of sheep and pigs and chickens. So patronising and irritating to teh Almighty, I should think.