Battle with Your Current and Future Self
Yes, that doughnut sitting in the break room is extremely tempting. You know if you take a bite out of it you'll enjoy it even if it is short-lived. Once you've finished that doughnut, you'd wish you hadn't eaten it. All that fat and sugar just went into your body and the next thing on your mind is working extra hard at the gym after work.
This is the struggle between your current self and the future self. Your current self just thinks about the here and now. While your future self is more concerned about what will happen hours, days, or even years from now. It's difficult to reason with your future self and more often than not your present self wins out. After all, there is no one to stick up for the future self in the present.
The problem with commitment devices is that without them you might feel like you lack self-discipline. The moment you get your credit card back you could go on a spending spree. There will be nothing holding you back. If that isn't enough, then you will also be tempted to find out ways to weasel your way out of things. For example, say you've locked your credit card away, but there is a one-day sale going on at Macy's for a great jacket. Although it is still priced above your price range, you rationalize that it will be more expensive later, so you better buy it now. Well guess what? You broke your commitment device.
One alternative way to give your future self more of a fighting chance against your present self is by imagining your future self. The moment we picture what our lives will be in the near future is when we start to understand and see what potential consequences might arise from our decisions. Seeing an aged self brings into light what reality may be like years from now. When you start thinking about your future self that is when you will think about whether or not you should eat that doughnut.
Specifically, Daniel Goldstein speaks about ways to help people save money. He has created software that models varying financial levels one can achieve at retirement based on a person's savings rate. On one end of the spectrum he shows an younger self and on the other side a picture of an older self. Save too much and your present self may be discontent, but save too little and your future self will be discontent living in a small apartment. Finding the right balance is the challenge, but live for the present and plan for the future.