I am learning to make exercise a normal part of my day, the same as taking a bath, brushing my teeth, and eating dinner. It shouldn't be something that you pencil into your day, just so you can have the option to erase it later.
From my blog: Would we contemplate taking a bath that day, because something came up? Or would would we say, "I'll just brush my teeth twice as long tomorrow, to make up for not doing it today"? Sounds ridiculous, right?
Let's quit letting life get in the way and make it part of our life instead!