Life is going to be even tougher now for Sugar Ray Leonard. The courage and skills he showed in whipping Thomas Hearns for the no-ifs-ands-or-buts welterweight championship has made it so. He will find it very difficult, if not impossible, to find enough demons outside the ring to inspire him inside.

It seems to be more and more important for Leonard to develop a severe mad for people in addition to his immediate opponent. In the past, the repulsive Don King and Bob Arum have been useful. The Hearns fight showed Leonard can make his millions without them.

Critics, inside boxing and beyond, have helped stoke the Leonard fire.

"When I use the term 'they,' " he said in Las Vegas the morning after his latest night of glory, "I mean the boxing critics, the ones who say, 'Sugar Ray Leonard's not supposed to do this,' or, 'He can't defeat this guy or that guy.' Guys who are quite significant.

"When I do that, when I defeat these guys, then they look for someone else, something else. I'm like a diamond." Here he paused, then said:

"In mud."

A diamond in mud. Hmmm. He looked at Hearns standing at his shoulder during the press conference and said that would happen to him, harpies snapping at him for everything from his ring manners to not giving enough back to a community that raised him.

Most of the wide-circulation magazines and newspapers forecast Leonard beating Hearns. Of course, Dave Jacobs and some longtime sparring partners were in the Hearns camp. In retrospect, this may have been as valuable to their former boss.

Now?

Ray, I think you've beaten most of your critics as badly as you did Hearns. Ferdie Pacheco is one. He had said: "I go with Hearns. My gut feeling is that it is show business against boxing, Joe Louis against Ali. Leonard is thinking of the Carson show and Hearns is thinking of boxing.

"That single-mindedness gives Hearns the edge. He'll be throwing bombs at Leonard all night, and one will connect. He only needs one while Leonard will need a hundred."

Leonard's hundred prevailed. And his mental toughness no longer can be questioned, not after that fistic flood that drowned Hearns after Leonard's left eye was all but closed after the 12th round. There simply is not an ounce of quit in this guy; many of us realized that after the first Duran fight in Montreal.

Days before the hit of the Hit Man, boxing's oracle, 73-year-old Cus D'Amato, who had questioned Leonard's will before Duran I, said, "Leonard won't let (Hearns) get away. Leonard is one hell of a finisher, like Robinson." Randy Shields, the only man who fought both Leonard and Hearns, picked Leonard.

Perhaps Leonard will be able to find future fuel from those of us who would like him to quit, walk away with both his millions and his senses. I thought he proved all he needed to during Duran I; the man closest to him, Janks Morton, thought that after Duran II was the proper time to retire.

Probably, Leonard takes this the wrong way, as questioning his manhood, doubting his ability. That's not so at all. Professional sports, boxing especially, should be used as a means to an end. Like any business, it should be treated as the route toward a more comfortable life.

Some of the men I respect most are former athletes for whom sport was a lucrative interlude in their lives, between adolescence and what they either enjoyed doing or wanted to accomplish long range.

Boxing is the sporting equivalent of working the mines.

I think Leonard is hooked. I sense that happened after he humiliated Duran, made the meanest creature in the ring appear to be cowardly. He wants to be one of the immortals, and who is to say that is wrong?

Mike Trainer, his financial adviser, has said Leonard wants to be known for his boxing skills more than for his show biz flair. Having darkened Duran, beaten Wilfred Benitez and humbled Hearns, that should have been accomplished. Anyone who still thinks otherwise should be dismissed as a fool.

Maybe Ray will pay attention to them anyway. Maybe he will hear doubting voices others of us do not hear and drive on because of them. He seems to want Marvin Hagler badly, to win titles in three divisions (welterweight, junior middleweight and middleweight). That is at least a year or so away.

His place in boxing history, near-universal adulation and affection, means much more than money to Leonard. That was obvious after Duran II. Even in the 1976 Olympics, as an amateur, Leonard fought desperately with aching hands.

For many of us, Leonard has a Arnold Palmer-like magnetism. He bestrides his sport at times. As with Arnie, we would like to see Ray leave as gracefully as he entered, with his luster still radiant. As with Arnie, we will understand why he might not, and keep tagging along.