Forget being promoted to CEO, becoming a Premier League footballer or designing a best-selling app: Nothing quite makes the man like fatherhood.
Suddenly there's no time to fret over how the rest of the world sees you. It all comes down to the opinion of one person who's tucked inside a soft blanket, waiting for a cuddle.
Parenthood requires boys to turn into men, no matter who they were before.
As Brad Pitt explained after becoming a father for the first time: "It changes your perspective. You can write a book, you can make a movie, you can paint a painting, but having kids is really the most extraordinary thing I have taken on."
"It's the best thing I ever did," added the actor in an interview with NBC's Today Show back in 2006.
Other celebrity dads have expressed the same sentiment. Even those with the most hyper-masculine images.
Action movie star Bruce Willis famously commented: "Stay home for the first year, don’t go anywhere, just be there. Play with that baby every day."
Fertility experts say that many men experience a drop in testosterone, after having children. And it's this hormonal change that helps guys to change their priorities and shift focus towards the child.
Fatherhood, it seems, is the great equaliser among men, turning movie stars and mail men alike into mushy parents -- which is one of the main reasons we love to celebrate it every year.
Officially founded in America in the late 1960s (where every third Sunday of June is now a national holiday), the day has since become popular all over the world.
Interestingly, Father's Day isn't just for, well, fathers, but in lieu of absent dads, it is also to celebrate grandfathers and fathers-in-law, explains HuffPost UK Lifestyle in a recent post about the day's history.
So in honour of dads everywhere, here are 22 reasons why we love our fathers...