A Clue, Maybe?

Today is proving to be difficult...I'm still feeling the effects of what happened the other night, which doesn't surprise me much.  I was okay this morning but seem to be very meh right now.
Hoping for any clue on my trigger, I put up a description of what happened on the depression boards.  About three hours ago I got a response from Emerald66 that might explain why things went down as they did:
"My dads 80th birthday was a contributing factor to my depression. Maybe this might sound odd but it hit me that he's getting old and one day he'll die and so will my mum, its like it dawned on me that they arnt going to live forever. This then makes you look at your own life and where its at and it feels like the song by talking heads : "once in a life time"http://www.youtube.com/watch?v=I1wg... You not liking your birthday on the horizon suggests to me you feel like with each year thats gone by lately, your not happy with what youve achieved or not achieved in that year. Looking at your mum and her being happy with her lot at 63, your wondering how you feel when you get to that age."
Okay, true.  But it doesn't seem to just be when I hit 63...it seems to be much sooner than that, like when I maybe hit 40 (which is a heck of a lot sooner than I think).

I think Emerald is right...but...I know how my state of mind tends to run, which generally isn't that positive...so...how do I reverse that?