This one seems like a no-brainer to me, but as I think about it, maybe other people will be inspired.
I live off of writing things down - work, blogs, and especially lists. I don't know if I have a bad memory or am just too much of a worrier, I have to write everything down to make sure that I remember to do all that I want/need to do.
I have always been a planner, from deciding what I'm going to do this weekend ahead of time to make sure that I'm not left hanging to thinking ahead years in the future. It doesn't always work out as planned, but I like to at least have an idea of what I am going to do - even though sometimes God has different plans.
I thinking planning and staying organized with lists is important, because you won't forget to do what you need to do. You won't forget an important ingredient at the grocery store, and you won't forget to pay bills. I think planning is responsible.
However, I used to plan to the point that I didn't leave room for anything other than my plan. Recently, I didn't plan for my car to break down, and I didn't plan to miss my alarm and forget to get up on Christmas Eve for the drive home. However, I tried not to freak out when my plans went awry. Sometimes situations go wrong.
You have to leave room for God to make his moves. He doesn't always have the same plans that we do, and we have to accept that whether we want to or not.
Also, planning can sometimes make people stiff and unflexible. Spontaneity can definitely make days more fun, when we go on a random trip or take time out of our responsibilities to spend time with friends.
Be responsible with your time, but also leave room for God and for fun.