In some parts of my lawn, the grass is thick and green. In other areas, it's sparse and dry. There are even a few places where the grass is missing entirely.
When I mow the lawn, I notice that where the grass is healthy, there are no weeds. Where the lawn is sparse, there are a few. Where there's no grass, the weeds flourish.
Every time I notice the weedy spots, I think, I really need to pull those things. So I do, but within a few weeks they're back—and I'm pulling them again. One day it hit me: I don't have to pull weeds where the grass is thick. Instead of spending all my time pulling weeds, maybe I [need] to invest time making the grass as healthy as possible. The more grass I had, the fewer weeds I'd have to pull.
The same applies to worry. Worry is like the weeds. God's peace is the grass. Instead of just focusing on eliminating my worries, I [need] to cultivate God's peace.