Memento Mori: Remember that you will die. This is an ancient idea that has been used by a lot of great people to enhance their lives. It has also seen a resurgence in modern times, aided by the revival of the philosophical school known as stoicism.
It seems counterintuitive that thinking about death would improve your life, but this forces you to reconsider your time left on earth (or Mars, if we eventually get there), and how well you are using it.
When you realize that you should use each day you get as well as you can, you gain more purpose, more vigor. However, us humans tend to forget about our mortality. This is why having reminders in your environment helps.
Memento Mori for Mac
https://itunes.apple.com/ro/app/memento-mori/id1393834268?mt=12
The app I made sits quietly in your menu bar, and shows your current age, and how it slowly increments, slowly, all the time. You can also set it to show the time you have left until your expected death (this seems somber, but it actually is the best productivity prompt I have found).
Memento Mori for iOS
Similar to the Mac version, this sits on your home screen as an icon and as a widget which shows your current age, slowly incrementing. You will find yourself glancing at it during your busy schedule and being reminded to focus on what really matters to you.
https://itunes.apple.com/us/app/memento-mori/id1399753137
If you are interested in using your time well, I’d appreciate it if you gave these a try!