The thing about fortune cookies is that any fortune can become real, provided the person who read the fortune can successfully convince themself that a given event fits the fortune. This is partially due to a psychological phenomenon known as the Barnum effect.
The Barnum effect is defined as "the tendency to accept certain information as true, such as character assessments or horoscopes, even when the information is so vague as to be worthless." The effect is also sometimes called the Forer effect, named after the professor who initially tested the phenomenon. Forer gave his psychology students a personality test, telling the students that he would give each one a list of statements about their personality based on the results of the test. The students then rated the accuracy of the statements he gave them. On average, the students rated the accuracy as 4.3 out of 5, an extremely accurate assessment-- only to learn that each student had received the exact same list of statements, which Forer had taken from an astrology book. Statements such as "You tend to be critical of yourself" and "Some of your goals tend to be unrealistic" are vague enough that just about everyone will agree with them, and therefore consider the source of the statements reliable. This is how horoscopes work.
With fortune cookies, it's usually not so much a personality assessment as it is, well, a fortune. However, the same principle applies. If the fortune is vague enough, then anybody who gets that fortune will probably be able to come up with at least one event that "confirms" it. Say Anna, Bree, and Chase each open a fortune cookie that says, "In your near future, a sudden windfall will come from an unexpected source." The next day, Anna finds $20 on the ground. A week later, Bree wins a college scholarship she hadn't realized she was eligible to win. And a month later, Chase's old uncle passes away and leaves him a fortune. Any of these events could be said to fit the fortune, so chances are that Anna, Bree, and Chase will all consider the fortune to have come true, regardless of the fact that it's vague enough to apply to three different events, and the fact that these events may have happened whether or not any of them had opened the fortune cookie in the first place.
Now, with regards to your fortune. It appears specific, especially since you have a specific and frightening event in your past that is on your mind, but it's still very vague. An "acquaintance from the past" can mean any number of people-- an old friend who comes into town and takes you out for lunch, a coworker you run into at the grocery store, the plumber you hired once to fix a leaky pipe. Any of these people could fulfil the criteria of the fortune and convince you that it was accurate. But these events could have happened with or without the fortune. The fortune itself can't affect your life-- only your perception of it.
TL;DR-- Fortunes are only "accurate" in that they're so vague that just about everyone who reads one will experience an event that seems to fit it, therefore convincing them that the fortune "came true." However, fortunes have nothing to do with anything that happens-- they just convince your brain, as soon as something does happen, that they were right all along. Your fortune doesn't mean that someone from your bad past will reappear in your life-- it doesn't mean anything. It's just generic enough to apply to a situation you've thought up. (And if someone from your bad past *does* reappear in your life, it had nothing to do with the cookie.)
I hope that wasn't too long and convoluted! ^-^