Abdul Qadir Gilani (ra) said, “In the month of Sha’ban every Muslim should clean himself by repenting and asking forgiveness for the sins of the past, and prepare himself for the month of Ramadan. In this month, Muslim must plead Allah (SWT) with petition and invocation, firmly follow and strictly hold the Sunnah of the Prophet (PBUH) and say lots of Salat u Salam to him for the rehabilitation of the heart and to cure the diseases of it; and then achieve to meet Allah. Repentance and asking for forgiveness should not be postponed for tomorrow.
Because the days are three: One is the yesterday which is already gone. The other is today which is the day of action, so we need to act and work. And the other day is tomorrow which only consists desire. Because, you don’t know whether you will reach for tomorrow and live. The past day is a lesson, today is a gift, and tomorrow is a distress.
Likewise, the months are three, too. First was the month of Rajab; return to it is unthinkable. Other is Ramadan al-Sharif; its arrival is expected. But you don’t know if you will reach it or not. The month of Sha’ban is like a bridge between these two holy months. That is why you should see the obedience and worship in this month as a prize and a great gain.
The Messenger of Allah addressed Abdullah Ibn Umar (ra) and said:
“O Abdullah! Know the value of five things before they are replaced with other five: 1-Youth before the old age comes, 2-Health before the sickness comes, 3-Wealth before the poverty comes, 4-Life before the death comes, 5-Free time before the business comes.”
Source: Ismail Fındıklı, Faziletleriyle Gün ve Geceler (Virtues of the Days and Nights)