The important thing about committing to anything longer than 30 to 40 days is that it establishes a habit. A rule of thumb I have always observed is that it 
takes three weeks to turn practice into habit, intentionally or not.
Source: Georgiapol.com, April 28, 2020. Link.
It is a bit harder if it is something you do not want to do. I do not like to exercise, but I do like to eat. A lot. Life is often a series of tradeoffs. Exercise, especially at my age and with my family medical history, is the ticket to good eating.
INSIGHT: For some, the best motivator to exercise and good nutrition is surviving their first heart attack.