this is a quotation from the Talmud Yerushalmi, which is itself quoting another text that was found back then. roughly translates to "leave me for a day, and i'll leave you for two"

the text also gives two examples: "two people, one of whom came from tiberias and the other from tziporin, and met each other in a shared residence -- they didn't have an opportunity to say goodbye, before one walked a mile and the other walked a mile, and now they're both two miles away from each other" and "a woman who was waiting for a man: as long as she stayed in his thoughts for marriage, she would sit and wait, but since he let his mind wander away from her, she went and married another"

it's originally given as a metaphor for faith and stuff like that, but i find that it works great as a metaphor for physical health/unhealth as well. for every day of neglecting to take care of myself, i get back not one, but two days of feeling shittier than before

when i feel ok, this thought can inspire me to keep going with exercises and healthy diets and stuff; but when i already feel like shit, it usually just frustrates me to be reminded that even if i do go back to taking care of myself, it'll take a while before i start feeling the effects again