I've worked with people who deliberately give less than their best, even in their lame excuses. "I'm hung over, I'm tired, I guess I'm under a lot of pressure..." well boo-flipping-hoo! I heard once of a hung over cook who was asked at what percentage she thought she might be operating, the morning after a bender. "Sixty per cent," she replied with a moan. "Great, that's what I'll pay you," said her boss. "Sixty per cent of your hourly wage." She perked up and if she ever came to work hung over again, no one knows and no one cares.
I knew a manager who used to ask us, "If you paid $100 for a ticket to see a performer and they just 'phoned it in' (gave a mediocre performance), would you feel ripped off?" Naturally, any of us would. "Well," he'd say, "Those people pay good money for a meal at this restaurant. Give 'em what they came for! Every time!"
Play full out. "Verso l'alto", my friends, in all that you do. Head toward the top.