I think you should keep a daily diary.

I doesn’t have to be exactly a diary though.

You can make a list, write down a funny line you heard, scream an opinion, or document a thought or an event, even draw a picture.

Derek Sivers says it all in this post.

I particularly like his suggestions on topic journals:

There are certain subjects in your life you think about a lot. People, places, hobbies, health, plans, finances. For each subject that you might have ongoing thoughts about, start a separate “Thoughts On” journal. Whenever you have some thoughts on this subject, open up that file, write today’s date, then start writing.

The point here is that, I think, a life lived is a life worth documenting.

I think it will make you look at things differently.

But if anything, you know what? Your kids and grand-kids will love it.

This passage by Sivers sums it up:

I find it so useful to keep my thoughts on each subject together, because I can see my past thoughts and current thoughts in one place. I can see how my thoughts on this subject have evolved or keep repeating. Sometimes I think I have a new thought on a subject, so I open up the file and write it down, then afterwards I see I had that same thought a year ago and had forgotten about it. If you care about your thoughts, keep them.