As Peter already noted, the best way to get back on track is to write down as much of the 'design' as you can - before you forget how you coded it in the 1st place.

One 'paranoid' backup method which I use is to register for a few 'free websites' & place password protected zipfiles of vital source code onto these. Then, your key routines are only an ftp download (and a password) away - no matter where in the world you happen to be working.

Derek