To deal with, manage, or do something oneself, especially after having relied on others to do it (and perhaps deeming that they did not do it properly or sufficiently). Often used with "matters." This project isn't being managed properly, so I'm just going to have to take matters into my own hands and start supervising the work directly. It's time to take your schoolwork into your own hands—you can't rely on your friends to help you with every class.