Ain't no sense like bought sense

This means that anything that you learn a life lesson from (that also costs you money); you will NEVER let it happen to you again.
For example..Loaning someone money a second time when they didn't pay you back the first time. Or getting the same girl pregnant twice when she told you she was on birth control..Now you are paying child support TWICE.
Or catching an STD from trusting someone who has told you "You're the only one I have had sex with." Meanwhile, you are spending money on doctor visits and antibiotics.

Man, I promise you I won't sleep with her again! She lied and said she was on the pill. Ain't no sense like bought sense!