What do you think of positive affirmations & gratitude journaling? Do they help?

If you walk pass my one of my colleague's desk or cubicle you wont miss it. It's "decorated full of positive affirmations of all sizes. Some in very pretty postcards, others in small tiny cards. The messages are pretty diverse, but all very positive, inspirational & encouraging. We always wonder if it helps. She has been the same since day 1...lol... Intense & quick to snap at her boy friend. She's very nice to us though. Maybe he deserves it. I know guys can be very annoying.

Then we noticed something else on her desk the other day. She has a book of some kind. It says Gratitude Journal on the outside. Wow !!! It's trending I guess. People are keeping them. Not sure if things like these works. The encouragement is there I guess, but how much of it will seep in? I ask her about it & she let me have a peep. It's cute.

She'll note something small on it everyday. Things like "I am grateful that there's no traffic jam today" or yesterday's entry was " I'm grateful that I can share this with my friend " ..lol... that would be me!

Should I keep one as well?
It wont hurt I guess.