Don't be a slave to your system.
If by "Most important thing I have to do right now" you mean that it is too important to wait, then you renegotiate. To heck with where you put the next action on your list a week ago. Change it.
If you need to call your brother now-as-in-now, and you don't have a phone, then your next action isn't "Call," it's "Go get my phone or find a payphone, borrow a phone or build one out of scrap metals like E.T." You have to change the next action in out-of-the-ordinary circumstances, and also if you renegotiate the agreement and outcome.
The trick is it's a lot easier to change the next action from the wrong one to the right one than if you have no action defined at all. You're not going, "What am I going to do about that situation with my brother?" for two weeks.