I use the 5-minute journal daily, morning and night. In the nighttime entry, it makes you ask yourself, "how could I have made today even better?" I seem to interpret this as "what did I regret doing or not doing today?" In these micro regrets, as all other regrets, I find that it is always something I did not do rather than something I did do
Rather than waiting until the end of your life to find out what you wished you had done, you can do this in advance or at least react quicker than waiting until your deathbed.
If you think about what you would have done differently each day, using the 5-minute journal or otherwise, after a year you have 365 micro regrets. If you analyse them I bet there is a pattern. Use this to not have the same regrets the next year.
Of course, you can do this even faster. Review the last month. The last week. Make sure you put something into action today from yesterday's micro regret.
Why wait until the end of your life, when you cannot change anything? Use micro regrets to ensure you don't have any later. Live in the present.