The phrase "in a rut" means to be in a state of monotony or routine, where one is doing the same thing over and over again without any excitement or variation. Full definition
It is easy to get stuck in a rut of what you've always done and not really know how to update your look on a budget, even if you wanted to. (theinspiredroom.net)
I think spinach is a GREAT green to add in smoothies, but I think sometimes we get stuck in a rut of ONLY using spinach. (thediva-dish.com)
There's so many of us that get stuck in a rut with fashion, makeup, and hair! (chicover50.com)