I've been journalling for 10+ years. In addition to forcing me to actually write down what happened that day, reviewing old entries provides a feeling of history that makes life feel soooo long and so rich. I can review my now-wife's rocky courtship and feel grateful we made it. I looked back 3 years ago and found the day our children were conceived :D (we have twins). I can review the anxieties of my PhD years, etc…
You're apparently in a good place so looking back is your path to your joyful present. I'm in a bad place so looking back is my seeing back when I was still hopeful for my various life goals. I'd meet someone and have someone to share my life with, do activities with, travel with, raise kids with, etc. I never met that person and now at 60+ that's nearly impossible so looking back hurts. It hurts a-lot. Seeing the op…
But that said, there’s alot of philosophy and other things to help. Aeschylus said “Happiness is a choice that requires effort at times.” Another relevant quote is that the best time to plant a tree was 20 years ago, the next best is today.
You won’t get what you wanted, but live in the present and enjoy what you can have. I’d give anything to get my wife back, but that’s not reality. The next best thing to live today and find joy.