But physical endurance and tough conditions eventually take their toll, and after 14 years in the Royal Marines, my boyfriend Peter's body was beginning to suffer.
Gastro-enteritis caused by drinking stream water and eating worms and grass during survival exercises had weakened his stomach.
He'd caught amoebic dysentery while serving with the United Nations in Cambodia and again during Operation Haven in Kurdistan. To top it all, he got cholera, dysentery and salmonella in Sri Lanka.
He doesn't like to complain, but the stomach cramps were so excruciatingly painful as he flew back to Britain from Sri Lanka that he couldn't even muster the strength to sit in a seat and ended up lying in the aisle hugging his knees.
He returned to his job, but the pain was so severe that he eventually sought medical help. Cholera was diagnosed and he was immediately hospitalised in an isolation ward. Doctors said his stomach was badly damaged and would take at least 18 months to heal.
Peter is the sort of person who normally likes to consume hot chilli washed down with a few pints of beer; but after just one pint, he said he felt terrible, as if his stomach was red raw.
After several months of Peter's chronic diarrhoea, I couldn't stand it any longer and set about trying to find a remedy. I suggested a faith healer, having friends who'd been successfully treated for similar complaints, but his response was sceptical.
The thought of going to what he called a "voodoo doctor" was too much.
Shortly after this conversation, I actually met a married couple who specialised in New Age spiritualism, including faith healing. Under duress, Peter agreed to go. He said was doing it to humour me and also thought it would be wimpish not to confront his fears.
All the same, he was a nervous wreck as we drove to the couple's semi- detached house in Kent, and I had to practically drag him by the arm inside. To his relief, they seemed to fit his idea of "normal"; Keith watched football on television while Fiona made us a cup of tea.
After about 10 minutes of polite chat, Peter was asked to sit in a hardback chair and to close his eyes. New Age music was played while Fiona and Keith stood over him, their outstretched hands a few inches away from his body. Later, he told me he had been nervous, but recalled a warm sensation as Keith held his hands near his stomach.
The healing session lasted about half an hour, after which Keith said he thought he could help Peter if he returned for five more sessions. He only wanted to charge pounds 5 a go, but we paid pounds 10. To Peter's amazement, and I think horror, Fiona then continued to diagnose further ailments. She'd detected something in his chest and asked if he'd been trapped under water. She also inquired about a knee injury.
He'd been trapped under water while diving and had damaged his cartilage playing sport.
But that wasn't the end of it. She wanted to know if he'd ever known an old man who wore a hat and had a dog, because this man was watching over him from the grave. Yes, his dead grandfather had had a dog - but then so did many people.
By this time, Peter was looking decidedly uneasy, and I knew that unless I got him away quickly, before any more ghosts were mentioned, he'd never return for more treatment.
That evening, Peter abstained from drinking. He said his stomach felt really sore, as if the rawness had been activated. Never the less, he booked another appointment, and this time he went alone.
Six weeks and half a dozen sessions later, Peter said his stomach was more or less healed. He says he would wholeheartedly recommend faith healing to anyone. He can consume alcohol and spicy food without pain, but he still hasn't risked a vindaloo.
The National Federation of Spiritual Healers can be contacted on 0891 616080.Reuse content