For singles matches, my focus would be:
Before the match - strategy/game plan especially if known opponent and based on surface, time of year/day, conditions. Visualize some point patterns that play to my strengths.
Between games - quick thoughts about what is working, what is not working, what point patterns are happening, what opponent’s strengths/weaknesses/preferences are, what tactics to adjust, adjusting to conditions (wind/glare/humidity/temperature/surface/condition of ball)
Between points - what serve (target/spin) to hit, where to stand on return and maybe where to return if FH/BH, what opponent is doing, quick thought about what happened in last few points and if any adjustment needed. Sometimes might think of whether any technique or footwork adjustment need to be made to adjust to conditions, opponent’s tactics or unforced errors I’m making. Do some visualization and silent mantras if behind during service games. Adjust breathing and leg activity (like jumping) to control stimulation level to optimal range.
During point - focus on shot selection decision (target, pace/spin, trajectory) of next shot with focus on getting point pattern in my favor and then execute without thinking.
For doubles, I would also focus on communicating with my partner and showing support/positivity between games and points. General attitude during matches will be to keep my intensity/focus high and try to be at my best from first point to last - usually this means keeping emotions in check and staying rational so that I’m able to think and adjust to my opponent/conditions quickly throughout the match.
During practice, I might think of checkpoints during shots and more about technique, but during matches I feel it is better to focus on just execution during the shot.