My problem comes in with the fact that "later" happens a very long time after the initial need of fixing. This is why I have an entire drawer full of mending--missing buttons and ripped hems; and even an alteration or two.
I decided recently that I was going to address my procrastination by tackling one or two items a day (or every other day as the case may end up being) until I completed my "fix-it" pile. So...over the past week I have re-hemmed three garments (one skirt and two dresses). [One of the dresses ended up being too small--yes, it's been there that long--but I got it fixed anyway.] And I have re-attached two buttons (two different tops).
My next item on the list is a dress I made just over a year ago to wear to a friend's wedding. I am going to rip the lining out from around the armholes and re-stitch it. I messed it up when I originally made it...only I didn't realize that until I was complaining about the binding in the armholes (to which I am hypersensitive) and my sister looked at it and told me what was wrong.
We'll see how long it takes at this rate to finish. :)