When the Muslim has the blessing of free time with which Allah has honoured him, he can do no more than look for the best deeds with which to fill his time, not just any good deed. Hence you see that the Sahabah/Companions (may Allah be pleased with them) asked the Prophet (peace and blessings of Allah be upon him) in many hadeeths (prophetic narrations) about the best actions by means of which they could attain a higher status before Allah, and the Prophet (peace and blessings of Allah be upon him) answered their questions.
The Prophet (peace and blessings of Allah be upon him) said: “There are two blessings which many people do not make the best use of: good health and free time.” Narrated by al-Bukhari (6412).
Ibn al-Qayyim (may Allah have mercy on him) said, speaking of regret about time:
Regret for wasted time should be deep, for time passes quickly and it is difficult to make up what you have missed.