"I'm probably talking too much," Jimmy Carter kept saying to a small group of visitors at the White House the other night. The visitors were journalists, and they only egged him on.

But the effort at self-discipline struck home. Carter is fighting that chief nemesis of presidents - euphoria.

To be sure, he wouldn't be human if he didn't feel up these days. The Camp David accord between President Anwar Sadat and Prime Minister Menachem Begin is now moving toward a rapid and dramatic denouement. The Knesset vote on Wednesday is favor of allowing the Israeli government to remove settlements from the Sinai Desert sets in motion the followup negotiations. So much of the detail was done at Camp David that only a few points remain to be completed.

Sadat seems to be pressing for a signing ceremony, perhaps on Mt. Sinai itself on the anniversary of his trip Jerusalem - Nov. 19. Carter will probably be on hand for the occasion and ride in triumph through Cairo and Jerusalem.

An equally fair prospect presents itself in dealing with Russia. Carter has put behind him the pressure of hawks inside his administration and outside to confront Russia in Africa or on military matters. The Soviet leader, Leonid Brezhnev, has equally put behind him the hard-liner pressure that led to the trials of Soviet dissidents and resident Americans.

Negotiations for a second-stage strategic arms limitation treaty (SALT II) are practically complete. The positions are so close, Carter told his visitors, that "except for pride of authorship" it wouldn't make a lot of difference whether the U.S. accepted the latest Russian offer or the Russians accepted the latest U.S. offer.

Presumably the treaty will be signed in the next few months. The occasion will be the one foreign-policy event apt to send the president's stock soaring still further - a summit of the superpowers.

On top of all that good fortune, there comes the likelihood of a strong finish to the 95th Congress. Thanks to the leadership of Speaker Thomas P. O'Neill, Carter has at all times been in relatively good shape in the House of Representatives. The favorable vote on the natural-gas bill last Wednesday suggests that he is now in equally good shape in the Senate.

The natural-gas vote testified to the power of joint effort by the adminstration and Majority Leader Robert Byrd (D-W.Va.). Together they beat three of the few whales remaining in the Senate - Finance Committee Chairman Russell Long (D-La.), Minority Leader Howard Baker of Tennessee and Sen. Edward Kennedy (D-Mass.).

As a result of the win, Byrd has now established a previously contested leadership. "You couldn't ask for a better man to work with than Bob Byrd," the president said of him. Presumably their partnership will carry through a full energy bill satisfactory to Carter. If only because his threat of a veto has real sting, the president also seems likely to get an acceptable tax bill.

In these conditions, the instinct is to shout hallelujah and advance the claim of having been right all along. But for the time being at least, Carter is resisting the temptation.

He admits that his original plan for a comprehensive settlement of the Arab-Israeli conflict at a Geneva conference couldn't have worked. He confesses to having been "naive" in thinking the Russians would accept the deep cuts in strategic armaments he proposed to them in the first three months of his presidency.

He acknowledges that he did not understand the Congress when he entered the White House, and that he is still not good at horse-trading. He even sees that there is a problem - a lack of harmony - in relations between the White House and many of the Cabinet departments.

Circumstances, as it happens, warrant a little protective pessimism. The Egyptian-Israe*li conflict is only part of a much larger problem - the problem of oil and petrodollars for which nobody seems to have a good solution. Relations with Russia are due to enter the truly difficut period only in the next few years when Soviet military power peaks and the succession comes up for grabs. Carter has yet to grapple with the most important domestic problem - inflation - and the signs indicate that he and his advisers have not yet developed an effective program to curtail wage and price rises.

So a sober mood is the right mood. We will all be better off if this president, unlike Presidents Johnson and Nixon, can avoid the self-intoxication that so often goes with a burst of dazzling success.