You've bought yourself a lovely bar of handmade soap. Perhaps you bought it from the soapmaker at a craft market. Perhaps online or in a retail store.
What should you do to get the best out of that handmade soap? The most important thing is drainage. Don't let the soap sit in a puddle of water - eventually even the hardest bar of soap will end up a mushy mess if left. Use a soap rack or dish that allows the water to drain away from the soap.
Allowing the soap to dry out between uses will prolong it's life. A well made, well cured bar of soap should last a few weeks.
It can even be a good idea to have two bars of soap "on the go" and alternate them - especially if you have a busy bathroom.
Back to that lovely bar of handmade soap. Don't save it because it's "too nice to use" - you can always buy more. Use it!