The phrase "deep ruts" means getting stuck or being in a difficult situation that is hard to change or get out of. It refers to a problem or habit that is deeply ingrained and not easy to fix. Full definition
When we hit this time of the year I usually fall into a deep, deep rut of wearing only jeans or black pants. (viewfrom5ft2.com)
But we're not running our usual 600 - foot slalom because the multiple runs required to get good data create deep ruts in the snow that skew the results. (edmunds.com)
The only modification needed was a decrease in tire pressures, and the Bentley was able to carve deep ruts over crests while kicking gritty rooster tails high into the air. (Autoweek.com)