The game always reset after every 9 days, your objective is to get the pink and yellow bar to the max to unlock the final card to get the final ending, which is a HARD ass chore since you have to redo the game like maybe at least 4 or 5 times to get the true end then get the "endless" mode which is the same rinse and repeat for 9 days just to unlock scenes
Actually, there are a couple ways to avoid the slog if you're not averse. There is an option to cheat... in the option menu oddly enough. AND Cheat Engine works too, though I was only able to freeze her Stamina. Essentially you only need a few days to work through all the acts and get them maxed out. Then a replay is necessary to unlock some stuff that also needs maxed.
For the Cheat option, it essentially makes the progress much faster, MUCH faster. It's a check box in the bottom right of the option screen, and when checked will open a new little window below with several other check boxes. I have no clue what they do specifically, but I just checked them all to see what would happen.
If using Cheat Engine, you have to start from Unknown Value and work through it Increased Value/Decreased Value,Unchanged Value. You'll end up with 8 values for the stamina bar for the girl. I forget which color it is, but it's above the yellow bar on the bottom left.