Your medical school personal statement needs to sell. Every single word has to sell your reader and answer the question: "Is it worth my time to read one more word of this essay?" To be persuasive is to sell your reader on your next sentence, your next paragraph, your next idea of your medical school essay.
Remember that tension, like all techniques, is merely another tool for making your writing more vivid and interesting to read. However, if you do use it, you must make it clear to your readers that the events you are describing have some relation to your study topic. If not, they will be confused, will have to re_read to make sense of it and may end up feeling irritated enough to stop reading.