“And you, who are cleaving to G-d, you are alive this day” (Deuteronomy 4:4).
Chasam Sofer says that a person’s evil instinct tells him that he can never meet all the Torah’s demands all his life. Inasmuch as that is futile, one may as well give up the battle now. Moses tells us, “Don’t undertake an entire lifetime challenge. Just do it this day. Tomorrow you can deal with tomorrow’s challenge.”
If you tell an alcoholic that he can never drink again, that is too formidable a challenge. Taking it “one day at time” is doable.
A friend who was sober 43 years recorded every day of his sobriety. The day before he died he entered 16,472 days in his diary.