Some basic truths about us, some fundamentals: married, single, divorced, rich, broke, breaking in or holding on, the morning after Oscar, Tony or Emmy, or struggling along without recognition; whether we are newcomers, superstars, an enduring light, a flash in the pan, a has-been or a comeback king, from low self-esteem to insufferable arrogance - we are the seesaw kids. Kids who hold on tight and wait, wait for the call, the audition, the part, the review - and then we do it again. Those are the ground rules. You accept them if you are an actor. And you accept the demons.

One veteran character actor told me he is so excited when the job comes to a close. He takes himself and his wife to Martha's Vineyard and for four or five days he is in bliss. ''And then,'' he said, ''every time the phone rings, I am running up the dock like an old fool, thinking 'Oh, God, please don't hang up. I hope it is work.' ''I've got money now,'' he said, ''but that's no comfort.'' Another actor, 34 years old, told me when he's waiting he drives back and forth across the United States calling his agent every few days from phone booths. He has no money and no comfort. And another, convinced each time his illnesses are not hypochondriacal, drives himself to doctors' offices and waits for test results. One actress does health spas, another buys and sells houses, a third designs gardens. ''Dangerous things, gardens,'' she said. ''You never want to come out of them.'' A not unsuccessful man with an Oscar told me that when he is out of work an inertia so great overwhelms him that he is practically catatonic. He could not leave his home during one period for over three months. ''Why?'' I asked. ''Fear,'' he said.

And fear encourages the demons insecurity and uncertainty. An elderly actress was over for dinner. When we sat down she threw back a straight Scotch and said, ''You know what I did today? I did a general get-to-know-you, they call it, at a new agency I've just signed with. Look, I don't expect them to kiss my backside, but I have been at this for 38 years and I sat there as kids younger than my children said things like, 'She'd be great as so-and-so's wife in his new series' or 'How good are your contacts in town? Who do you know personally?' '' She was torn between her insecurity and need to be accepted and her anger at expecting and not receiving the treatment she felt her lifetime of achievement had entitled her to.

An agent once said to me when I mentioned I was in my third month of unemployment, ''How I envy you! You can sleep late; take the kids to the park; go on holiday.'' ''Why don't I take the keys to your office,'' I said, ''lock the doors, send home your staff and let you know when you can come back to work. Wait until I have something for you.'' He laughed, but didn't get it. How could he? How could anyone who has not experienced unemployment several times a year every year of his working life. No matter how often an actor may tell himself that a refusal is not necessarily a rejection, the word ''No'' only deepens his self-doubt.

And, even when employed, the actor is still stalked by uncertainty. A great Broadway star once told me that during the entire rehearsal period of one of her many triumphs, she got out of her taxi 20 blocks before the rehearsal studio and walked the entire way in order to stop shaking. ''I was certain I was going to be fired,'' she said. I recalled that when I was a young actor my famous leading lady asked if I would drive her to the first day of rehearsals out of town. ''Sure,'' I said, too cocky to be nervous myself. She got into my car; we drove three blocks and she promptly vomited. ''Wait until there is more at stake,'' she said. ''You'll know what it's like.'' And, as the seesaw rocked back and forth for me, I remembered her words.