Every day, two services - apps to which I subscribe - scan my social media feeds (facebook, twitter, instagram) and deliver an email to me that contains my posts from one day from the past.
Timehop sends my feed from exactly a year ago. It also tells me what the day and weather were like and if anything significant occurred. Best of all it gives me a pep talk, saying I'm awesome (or not) in a little note at the end of each report.
Offering a deeper look into your online life is Memolane - it too sends a daily email. Rather than limit itself to a single year, this service can reach back further and I find myself viewing tweets I wrote four years ago when at the age of seven, for example, Joe coined the word "republicat". I love being reminded of my son's quiet genius.
On the other hand, there is always a risk that I'll be reminded of a horrible day. In fact, it happens more often than I would like. Occasionally it gets me down, but more often I'm grateful for how far I've come.
There are other apps that are offering this service (foursquare, for one). Do you subscribe to any? Why do we find our own pasts so fascinating?