This is a spell I do over the course of a year, though you could adapt it to a different time period to suit your own circumstances. I begin afresh on 1st January, and quite simply each time I get to the last sliver of a bar of soap throughout the year, I put it in a drawstring muslin bag on the bathroom shelf. Personally, I like to suit the soap to the season, so in winter I may have a warming cinnamon and orange scented one, then a floral for spring, maybe coconut for my summer holiday and vetivert or patchouli for autumn... As the year progresses the muslin bag fills with aromatic slivers that each bring back vivid scent-memories of the past months. And then, towards the end of December (I judge this by eye, depending how full the muslin bag is) I begin to use the muslin bag to wash myself in the shower instead of a fresh bar of soap. The idea is that as we approach the end of the year, I am re-visiting and integrating the experiences of the last 12 months. It's pretty effective, as of course scent is a great catalyst to memory. It is also symbolic of washing away the last vestiges of the old to make way for the new. The important thing is to time it so that the last of the soap dissolves away on New Year's Eve. And then of course, a carefully chosen, fresh new bar can be unwrapped on New Year's Day, and the spell begins for another cycle. You could of course choose a different start/end date, your birthday perhaps, or maybe Samhain or some other significant date. You could even choose a different time period than a year, perhaps stretching the process over a period of difficulty (such as medical treatment, a legal battle or time of emotional upheaval) so that you can finally wash it all away as the period comes to a close.
I also recommend the cleaning the house on New Year's Eve/mindfully choosing your activities on New Year's Day spell. It certainly starts the year on a good note!
P.S. I have to confess I am particularly fond of the soaps produced by Lush, although local West Wales company The Soap Shed have some delicious products too.