I learned a great analogy from the speaker. When you invest your money instead of spending it, you may earn more in the future. The same is true for time. If you invest your time instead of spending it, you may gain more in the future. The key is to tell the difference between investing and spending. Doing something by yourself is spending, while train an algorithm or someone else to do something is investing.
When you say yes to something that you have to spend your time on, you say no to an opportunity of investing your time.