You must be very worthy to be able to meditate for a given time each day and regret what you must.
Not everyone merits such mental tranquility each day. The day may pass and go without time to reflect. A person’s whole life may pass without one ever once having time to really think.
Therefore you must make sure to set aside a specific time each day to calmly review your life. Consider what you are doing and ponder whether it is worthy that you devote your days to it.
Reb Noson of Breslov; Rebbe Nachman of Breslov. Rebbe Nachman’s Wisdom #47