Too Long; Didn't Read
There can be 3 triggers to a goal: Idea, Motivation and Action. Idea is the trigger that starts the process in your mind and you'll never act on it unless you're motivated to do it. Motivation is a chemical process in the brain. When we're motivated, our brains release dopamine, which makes us feel good and gives us energy to get things done. But when our motivation runs out, we don't have any of that dopamine left and so we feel tired and lethargic instead.