The 28-year-old, who switched nationality from Russia to Australia in March, lost badly to Sonay Kartal in her opening match at the WTA 1000 event in Beijing last week to make it three defeats in a row.
She now holds her lowest ranking since May 2022.
"I've been far from fine for a long time and truth be told, my results and performances show that, the fans aren't stupid, they can see it too," she posted on social media.
"I've kept a lid on my feelings because I don't want to seem like I am moaning, weak or god forbid ungrateful or unappreciative of this amazing life we live as professional tennis players.
"Truth is, I've hit a wall and I can't continue. I need a break.
"The schedule is too much, mentally and emotionally I am at breaking point and sadly, I am not alone."
The openly gay Kasatkina, who had criticised Russia's attitude towards LGBTQ+ people and described the war in Ukraine as a "nightmare", also referenced her change of nationality as a reason for her increased mental fatigue.
"Not being able to see my parents (four years now for my father and I), plus the ongoing battles to gain full Australian competition eligibility, it's a lot and there is only so much I can deal with," she said.
Kasatakina, who has won eight WTA titles, is now focusing her efforts on being fit for the start of the new season.
"I will be just fine though, and look forward to seeing you all in 2026, energised and ready to rock!!" she said.