Proverbs 21:20 NKJV
There is desirable treasure, and oil in the dwelling of the wise, but a foolish man squanders it.
Solomon said that unlike a foolish man, a wise man has treasure and oil in his house. The difference is the wise man values what he has and treats his valuables properly. The foolish has no sense of the value of what comes into his possession so he wastes it and ends up doing without.
Spiritual parallel: Wise people understand the value of the Holy Spirit and the anointing and do what it takes to maintain an abundant supply. The foolish person allows himself to be distracted and neglects doing the things to keep his dwelling full of spiritual oil. When we have used up oil in the storms of life, we must refill our vessels. Sometimes that requires extra effort.