A lot of life is about repetition. We wake up in the morning. Do some sort of workout. Eat. Get ready for work. Go to work. Daily grind, daily grind, finish some projects, eat lunch, daily grind, get off work. Make dinner. Eat dinner. Do dishes. Do a few small things. Go to bed.
Wake up in the morning. Do some sort of workout . . .
You get the point, probably because you do some iteration of it. Over time, we work ourselves into ruts. We eat this for breakfast—because it's what we always eat. We go food shopping at this time—because it's when we always go. We wear this dress to weddings, walk that route to school, listen to this music in the shower—because it's how we've been doing it for years.
Repetition makes some things better—if you write every day, little by little, you'll become a more clear, effective writer. If you paint every day, you'll be quicker, sharper, cleaner. If you chop wood, you'll get stronger. If you give IVs, you'll be faster. If you cook, your food will taste better (unless you always burn it or use bad recipes. But that's a different topic for a different day).
Repetition makes some things worse—if you fight with your husband (wife, brother, parent, neighbor) every day, you'll get better at fighting (and conversely, worse at agreeing, and relationships, and being friends in general). If you follow the same mind-numbing routine every day, it's easy to lose sight of the small beauties and tiny moments that make the humdrum magnificent.
There's a two-fold point:
1) Make sure you're repeating the right things. Choose the good things (creating beauty, loving, being kind) and scrap the bad (picking fights, disrespecting, being malicious). In the long run, when your character ruts run deep, you'll be glad you did. So will everyone else.
2) Remember why you're doing what you're doing. If you're creating (or any verb) every day, it's easy to become disenchanted with your craft. But when the going gets tough, remember why you began in the first place. Everyone has different reasons, but many artists share at least one: