add another string to (one's) bow

To gain another skill, ability, or offering. Luckily, I had added another string to my bow with my degree in graphic design, so I was able to pick up some freelance work when my hours were cut back at the office. A: "I'm thinking of taking up French." B: "Go for it! It's always good to add another string to your bow." I do have my real estate license already—yeah, my parents were adamant that I add another string to my bow in case my professional football career was short-lived.