You can’t always bring your best game to every task. In fact, if you tried it’d be wasteful. Not all tasks are of equal value.
So when to bring your ‘A’ game? Here’s a rule of thumb that’s been useful for me:
When you expect others to bring their best self, bring yours.
If you’re interviewing someone, you’ll ding them for not bringing their best. As the interviewer, if you expect them to come on the ball, so should you. Don’t rush in and lazily conduct the interview.
If you expect someone to do their best editing job on your writing, do your best composing it.
If you are OK with someone doing a B+ for a task, you can do the same. I don’t expect my wife to summon every one of her culinary powers every time she makes dinner, and I don’t demand of myself my absolute highest spic-and-span cleanup job after. It’s a B+ environment. If one of the kids is sick and it’s a crisis, I expect her ‘A’ game and demand my own!
If you want to know when to put in 110%, ask when you expect it of others.