Ant Middleton doesn't make eye contact with his son if he gets injured to try to prevent the youngster from crying.
The 38-year-old TV star - who is best known as the chief instructor on Channel 4's "SAS: Who Dares Wins" - says he is training his nine-year-old son Gabriel to control his emotions, but admits he is going easier on his daughter Shyla because he thinks boys should be tougher than girls.
Speaking to Giovanna Fletcher on her podcast "Happy Mum, Happy Baby", he said: "I do say to him, "Son, come on, you're a little man now, have a stiffer upper lip."
"If he was to fall over and hurt his knee and look up at me, I avoid eye contact. The moment he sees my eyes he's going to start crying.
"However, if it was my daughter, I'd be straight over there to comfort her."
Gabriel is a fan of Thai boxing, but when he gets hit his father tells him to "harness that aggression" and be strong.
Ant added: "If I take him, he'll get hit and I'll give him a nod as if to say, "It's OK son, harness that aggression and use it."
"That's life. It's not being sexist, it's not being non-PC. I'll say it how it is and, in my heart of hearts, I think I'm doing the right thing."
The former soldier previously described killing someone as "satisfying" and admitted it feels "like nothing at all".
Writing in his book "First Man In: Leading from the Front", Ant said: "Most people I meet don't have the courage to ask the question: What's it like to kill a man?
"Killing someone feels like pulling your trigger finger back a few millimetres. It feels like hearing a dull pop.
"It feels like seeing a man-shaped object fall away from your sights.
"It feels like getting the job done. It feels satisfying.
"But beyond that, killing someone feels like nothing at all."