NEW YORK; NOW FOR THE HARD PART

There were reminders of Nelson Rockefeller in Mario Cuomo's loosely sketched presentation of his coming budget and program at a breakfast forum here on Thursday. But there were just as many reminders that those flush and ill-planned days are over.

The new Governor confirmed that he would raise fees to help close the $1.8 billion budget chasm so as to make it less universally painful than broad-based taxes that fall on everyone. That was a Rockefeller specialty. But Mr. Cuomo also said he was going to cut 8,000 to 10,000 employees off the state payroll - something Mr. Rockefeller never even considered.

''It's not like the 60's,'' said Assembly Speaker Stanley Fink after the Cuomo presentation, ''where you were doing everything you wanted with all the money in the world.''

And while Mr. Cuomo noted the increase in ''efficacy'' when one rises from Lieutenant Governor to Governor (''Now when you push the stone, it moves''), he also prepared the public for his future compromises and losses by saying: ''It is the role of the executive to propose. It is the role of the legislature to dispose. ... The governor cannot make a law without the Legislature. I can't make a budget.'' These were things Nelson Rockefeller used to say, too, when he wanted to distribute the responsibility for the bad news to come.

So Mario Cuomo's honeymoon is over in less than a month, almost before he had any chance to enjoy it. In fact, I think it's reasonable to suggest that he will soon be wishing for some vacation time away from the wars of Albany.

Watching Mr. Cuomo outline his intentions on Thursday, it came to mind that the new Governor ought to take pains not to make his hard job any harder by adding a credibility gap to his fiscal one. On a couple of issues -his positions on taxes and on strikes by public employees - Mr. Cuomo seemed to waffle away from state-ments he made during the election campaign. Changing one's mind straightforwardly on an issue after taking office is one thing, but doing toe-dances around a semantic Maypole is to invite skepticism about the meaning of a promise or commitment. Mr. Cuomo's strongest suit has been his credibility; to fritter it away with debater's tactics - in an attempt to reconcile old stances with new ones -would be a serious self-inflicted wound.