It is the start of Lent today.
For Catholics that means the beginning of 40 days of self-sacrifice, mirroring the time Jesus spent in the wilderness.
Even people who are not religious sometimes give up things for Lent.
But therapist Leslie Shoemaker says they are being insincere.
He said: "For those who are doing it because they are following a religious faith, I really admire them, they know why they are doing it, that is not an issue.
"For other people who choose to do Lent, be honest with yourself about the motivation.
"If you're doing it to lose a few pounds, please don't go telling people you've given up crisps for Lent."