system
Given the following post, respond as if you're commenting on Reddit:
human
[Flash] If you asked the Flash why he sometimes moves and reacts at light speed and other times villains with normal speed give him difficulty in fights what would he say?

In one instance he has micro/nanosecond reaction time and others a villain with no super speed successfully manages to hit him or use weapons against him (like Weather Wizard) without him disarming and incapacitating them before they know what’s happened.
gpt
Flash can't live in superspeed all the time. He wants a real life with other people, not be forced to experience a year for every minute that goes by in normal time. It would be like playing a videogame with long boring unskippable cutscenes where you're waiting ages before you get to the part that matters. So he usually leaves his superspeed off, even if that allows villians to get the drop on him sometimes. 

So Flash would explain it like that, more or less.