Something Laura Kalbag said at Responsive Day Out last week:

“If you’re not ashamed about what you were doing three months ago, you’re not keeping up.”
If I could go back and rebuild every website I’ve ever build I would.

As it happens I am currently converting an ASP site I build just over a year ago into a PHP site. I could just replace all the ASP with PHP and call it a day, but that would be a missed opportunity. Instead I am using the knowledge and skills I have acquired since to improve the site and make it leaner and meaner (in a good way).

Should keep the shame at the door for approximately three months.