Pack Zipper

Why do i keep procrastinating about mending my back pack?
I have this favourite back pack which i made to beginn with and have been happily patching for years. It is developing a lot of charachter and i love it dearly. But a while ago the zipper broke and i got as far as taking out the old one but since then it has been sitting on the mending pile. why is it taking so long to get around to it this time?
go mend it RIGHT NOW