“You have some dirt on your face.” I often hear this strange remark from well-meaning people in the grocery store, after I attend Mass on Ash Wednesday.

This year, the big day marking the entry into Lent — a 40-day season of penance, prayer and alms-giving — falls on March 6.

During Mass, the priest places ashes on each person’s forehead, while saying, “Remember that you are dust, and to dust you shall return” or “Repent, and believe in the Gospel.”

The first admonition is a stark reminder that procrastinating about changing our lives can be disastrous.

It reminds me of a story about the 90-year-old man who was in the hospital and visited by a chaplain, who invited him to confess his sins and pray.

“I think I’ll wait,” the man replied.

Isn’t it tempting to believe we always have more time? That we’ll get our lives in order next year, or five years hence?

Clelia Merloni wrote, “We imagine that our later conversion will be easier, while on the contrary, our procrastination makes it even harder by weakening grace, strenghtening habit, hardening our heart.”

The second saying on Ash Wednesday urges repentance, which means turning our hearts back toward God. The prophet Joel wrote, “Even now, says the Lord, return to me with your whole heart, with fasting, and weeping, and mourning.”

There’s a mournful tone to Lent, since we ask God’s forgiveness for our sins, such as selfishness, gluttony, cruelty and lust, plus many others.

Still, this doesn’t mean folks should go around looking miserable, just because they turned down a hot fudge sundae or passed up a big sale at the local Stuff Mart.

After all, repentance isn’t about getting friends to feel sorry for us — it’s between us and God. As Jesus said, “When you fast, anoint your head and wash your face, so you may not appear to be fasting, except to your Father who is hidden.”

Over the years, I’ve been intrigued with how different people approach Lent. Yes, there’s the childhood promise to give up sweets, but some courageous folks refrain from gossiping and complaining, which can be tougher than turning down a chocolate bar.

Many people eat meatless, simple meals and watch the grocery bill shrink, which means more money for the collection basket marked for the poor — or they curb the impulse to buy stuff that gives them a temporary high.

Others sacrifice time by visiting homebound and hospitalized people, and attending daily Mass, where they pray for folks who are suffering. These stalwart souls often discover a cache of free time by turning off the TV and giving up social-media addictions.

Some things we give up for Lent can be cheerfully resumed on Easter Day, such as eating ice cream, drinking coffee and chowing down on hamburgers.

But some sacrifices, like quitting smoking, breaking a pornography fixation or cutting down on booze, can lead to a lifetime improvement.

It’s hard to give up things in a society that urges us to treat ourselves to whatever we want! Which is why prayer is the heart of Lent, because, really, how could anyone refrain successfully from lavish meals, TV and shopping without God’s grace?

And really, it won’t bother me on Ash Wednesday if some well-meaning person at the grocery store points out the smudge on my forehead.

You see, the most important thing about the ashes is they’re made in the shape of a cross, which reminds me that I belong to Jesus Christ, who is the center of my Lenten fast — and my whole life.