Which of the 6 project development phases do you think is most important?

The 6 phases of project development are:

1. Initiation phase

2. Definition phase

3. Development phase

4. Implementation phase

5. Follow-up phase

I believe the follow-up phase is most important because you need to look back on your project and see how it went.  Reviewing the good and bad parts of a project is necessary due to future developments and current changes that may need to be made. The follow-up phase with most types of projects is neglected often due to people not understanding the importance of this phase.