If I need to go to the hospital, I must face the unwelcome fact of my own vulnerability.

This is perhaps the first reality I must ponder if I am to be hospitalized. I -- or you or any patient -- must now confront our own illness or injury, our own mortality.

Even the healthy mother in the hospital for a normal childbirth must prepare herself for a challenge to her exposed body.

Acknowledging this is no joy, but it may help prepare us for modern hospitalization's other realities: noises, odors, other sick people and little hand-holding. The hospital is not a TV sitcom or adventure but a place where we mend or succumb according to our own strengths or weaknesses and the capabilities of the hospital staff.

Hospitals, at least those that can afford it, work hard to present pleasant, cheerful faces to the prospective patient and visitor, and this is all to the good. But we see this side of the hospital, we see the sanitized wards on TV -- with comic relief -- and the reports of medical miracles on newspaper pages and TV, and we may be unprepared for the true hospital scene.

"I'd forgotten that in a hospital you see people crying," said a woman who worked for a hospital in the South, spent some time in another field, then became an administrator in a Washington hospital.

"I'd forgotten how much can go wrong so quickly for some patients. I think it's hard for people to reconcile all the reports of medical progress with the realities."

The realities include getting well for many people, or at least beginning to learn to live with a disorder.

But they also include fear, anger, pain and feelings of depression and hopelessness, aggravated by a sense of helplessness and ignorance in a world of events we don't understand and few people explain.

"Pain can color the patient's whole life and make even the simplest task an awesome and grueling experience," Dr. Mark Rosenberg, a former physician in Boston hospitals, writes. Aids to pain may include drugs that, together with illness, cause disorientation and misperceptions -- the patient who is sure "someone hurt me last night" or "no one looked at me all day."

In a hospital, says Dr. Robert Coles, Harvard psychiatrist and social critic, we experience "the looks of resignation, of suffering, the sounds of one person after another trying to come to terms with life's relentless, messy challenges, which may threaten to break us, but -- psychologically, spiritually -- can also become the making of us, until we once and for all leave." (This from Coles' foreword to Rosenberg's sensitive "Patients: the Experience of Illness," W.B. Saunders, 1980.)

The hospital atmosphere is also an alien atmosphere that may be made more alien by our illness. The world of the sick, writes Dr. Eric Cassell (in "The Healer's Art," J.B. Lippincott, 1976), shrinks to "a small space, scarcely larger than his own body . . . Someone may be nearby but seem not to be there . . . Understanding fails, and sustained thought seems too difficult to achieve.

"All control of the world is gone . . . The bed is made while the patient is moved from side to side . . . The patient is dependent on all around him."

In the hospital environment, Rosenberg says, patients have "numbers, gowns, beds, charts, pills . . . operations . . . illnesses . . . problems . . . they've lost their sense of well-being.

"Even a healthy individual who is made to disrobe and lie down feels defenseless and despondent. When that person is ill, psychologically dependent on doctors and nurses, he may feel totally helpless."

And "hospital procedures and schedules confine a patient to his room so he can be available" for examinations and treatments. Hospital schedules may increase your "sense of loss of control" just as you struggle to regain control of your body.

Is all this too gloomy a picture?

Taken alone, yes. Most of us cope with disease and the hospital.

Some of us face illness by talking about it or trying to learn more about it. Some face it by denying it.

Even anger can help. Many doctors say angry, aggressive patients may get well more often than passive, accepting ones.

Some persons treat an illness with humor. Laughter interrupts "the panic cycle," says editor-writer Norman Cousins, now medical teacher Norman Cousins. He helped treat himself by watching Marx Brothers movies. Paging Dr. Hugo Hackenbush!

All these ways of caring may work or help. But almost all of us patients, we are told, can do better if we learn to face the hospital reality: It is a place to fight, not enjoy, illness.