A Ulysses contract is a pre-commitment with some sort of binding element; a promise you both make to yourself and force upon yourself.
It is named for the Greek hero Ulysses, who had himself bound to the mast to allow him to listen to the song of the sirens without going mad.
Examples of modern day contracts range from barely enforceable nudges to legally binding directives. If you have a hard time motivating yourself to go to the gym, you might schedule a workout with a friend, knowing that you won't be willing to skip out on them. If you know that you might lapse into a unsound mental state, you might prepare a psychiatric advance directive -- a close cousin to an advance directive or living will -- directing medical professionals in what they should do if you are found unfit to make decisions.
The term Ulysses contract (sometimes 'Ulysses pact') is becoming popular to cover many pre-commitment strategies. Things such as bariatric surgery, deleting Facebook from your phone, and payroll deduction to build retirement funds might all be considered forms of controlling your future self; at some point, the distinction between Ulysses contract and a simple choice becomes blurred. It may be more in the spirit of Ulysses to use this term specifically when you are binding your future self to do something that you know you will not want to do, through lack of willpower or mental stability. Setting up an automatic bill pay probably does not meet that criteria.
Other terms used include 'commitment device', or in the case of psychological directives, 'voluntary involuntary treatment'.