Have you ever observed that you can live through the same event with someone but afterwards you're reflecting and the two of you experienced something totally different? What you choose to focus on determines the experience that you have.
You have a lot of work you need to get done. You sit down to eat dinner and quickly eat your food, you aren't even tasting it because you're mind is thinking about what you need to get done.
You ride the bus with someone each day and after a year of doing so you realize you hardly know anything about them. All your small talk about the weather, the day's errands, the bus driver, and you never thought to get to know the real person.
Most of what you do in life you're doing on autopilot. This is okay, it has to be this way; your attention is so limited that you would be unable to get much done if you were in capable of automatizing complex behaviors. It's this ability to automatize which allows you to accomplish ever-increasingly advanced things.
However, the consequence of this ability to rely on autopilot, is that we cease to be intentional about our application of our conscious focus. After automatizing doing something well, it's easy to simply rely on that automatization and let our attention mind wander in the process.
Another example. A lot of people spend too much time over-optimizing things. Your confronted with a situation that has a lot of options and you spend way to much time applying your conscious focus to evaluating each and every alternative but the situation doesn't warrant it. Frankly, you would have been satisfied with any one of the options and you should have picked the first one and spent your time doing something else.
The most limited resource you have isn't time, it's your attention. Be careful what you apply your attention to. Apply it to those situations that you really care about, that are worth your attention. Don't bother to apply it to those that don't.
Know which situations you should be intentional about and which situations you should simply act out of habit. The ability to act out of habit is an ability which should not be abused.