I so agree. I thought I might share how I, personally, deal with life AND a gratitude journal.
I keep what I call my "ONE Notebook" back in the 1980's. I try to be diligent about reflecting on my day and finding, if not 3 things that I was grateful for that day, at least identifying at least one point in the day when positive things effected my day. I would, however, if the day was one of those "terrible-horrible-no-good" days start my reflection vomiting words about the spew of the day. Eventually, when all the anger, frustration, and hurt were gone, I sometimes found a bright spot in the day. Even if that consisted of my son giving me a hug or thanking me for picking him up.
In my mind, if we only focus on the negative that happened during the day, we miss out or consider insignificant the little gems that happen to us during the day.
By venting and looking for a positive not in my day, I allow myself to deal with both the bad and the good.