LPT: Even if (or especially if) you're an expert in your field, take time to peruse related ELI5 and other Q&A subs to see how others approach understanding what you do.

In addition to helping you explain "so what do you do all day" a little more easily, you might gain a new perspective on what you already know. It's said that you can't be sure you really know a subject until you can explain it to a five year old, or so I've heard.