One of the best ways to make a real commitment to do something is to sign a formal contract with another person. Such a contract should require you to put up something of value as "honest money." Such contracts have become popular in self-improvement clinics such as weight-loss or stop-smoking programs. The evidence is clear that people who put up some money that will be refunded if they fulfill their signed contract to attend the meetings are much more likely to complete the program and to attain their goals.
There may be occasions when making up your own contract can be helpful. For example, suppose you frequently fail to get up in time to make an early morning class. You can put money in an envelope addressed to some charity, and write on the back of the envelope the commitment that it should be mailed if you miss another class. Sign the commitment and give it to the professor, with the understanding that you get it back if you attend every class. You will find that when your good intentions are not enough, a contract will help.