Setting aside a few minutes on a regular schedule to write in a journal will give you a great source of ideas when you need them. What you write does not need to be long or formal. You can use a journal in several ways:
To record and explore your personal thoughts and feelings
To comment on things that happen, to you personally or in politics, in your neighborhood, at work, in college, and so on
To explore situations you do not understand (as you write, you may figure them out)