Fewer things are less pleasant than realizing you have an obligation that you forgot about.
For example: getting in all of your required hours at the library during the week, thinking that you didn’t have a saturday work shift. Then you go the library to work on the mountain of projects that you have due in the coming weeks, and your phone buzzes to remind you that you have a four-hour work shift from 1-5.
So you spend four hours at work that you couldn’t afford to spend and could have distributed throughout the previous week as free hours to make up for the block of time you couldn’t do homework on Saturday.
And it all could have been avoided if I had looked more carefully at my schedule.
So as always, the biggest obstacle to my own progress is myself.