You use touch-and-go about a situation that could still go badly wrong — it is not decided yet, and the bad ending is a real possibility. It is almost always used with 'it was' or 'things were': 'It was touch-and-go for a while.' Notice the past tense. That is the most honest thing about this word: people mostly say it AFTER the danger has passed, looking back on it. A doctor tells the family afterwards, 'It was touch-and-go last night, but she's stable now.' So the word carries relief inside it as often as fear. It is common about someone very ill, about a business that nearly closed, about a plane in bad weather, about a match either side could have won. It is a spoken, everyday phrase — not formal, not slang. You will hear it from a nurse, a coach, a boss. One more thing: the phrase does not point at one moment of danger so much as at a stretch of time when nobody knew. That uncertainty, that not-knowing-yet, is really what it names. When you write it as a modifier before a noun it keeps the hyphens — 'a touch-and-go operation' — and after 'was' many people write it without them: 'it was touch and go'. Both are fine.