take it upon (oneself) to (do something)

take it upon (oneself) to (do something)

To decide to do something even though it is not one's responsibility. I took it upon myself to print out these information packets for the meeting since I knew the data might be confusing. The kids took it upon themselves to wash your car—I'm so proud of them for doing it without being told!
See also: take, upon

take it upon oneself

Also, take on oneself. Undertake something, as in I took it upon myself to count the precise number of children in the audience, or She took it on herself to enter a convent. [Second half of 1400s]
See also: take, upon