The more clearly you can define your financial goals, the more likely you are to choose suitable investments for each one.
Goals become much more concrete, more real if they're formalized.
Without a written reminder, it becomes much harder to pay attention to them. Don't leave anything out. At least in the beginning, it's a good idea to put down everything you think you might want, no matter how farfetched it might seem. Acknowledging all your goals lets you assign each one the proper priority in relation to all the other wants and needs in your life. You can then develop a game plan for pursuing it or be honest with yourself about the fact that other things are more important.