Although your audience won't have had the same experiences as you (or there would be no point telling the story), they will be able to identify with elements of it. For example, you might start by describing your feelings before an important pitch meeting, and how you suddenly felt like you were back at school, standing outside the exam room waiting for the doors to open. Although your audience may never have pitched for a million-pound contract, they've all sat an exam, and will be able to remember exactly how they felt.
Some speakers introduce these common elements by saying "you know how you feel when.....", but I don't think that's necessary. If you tell the story exactly as it happened to you, describing your feelings and emotions at the time, they will identify with you. You will learn the phrases and analogies that work well, and also discover what will touch different audiences.
Aim to include three or four common experiences in every speech, and you will take your audience on a journey with you.