I used to have a goal, everyday at work make three people smile. Give someone a compliment on things they do all the time that goes unnoticed by most others, comment on their appearance in a postive way, give them encouragement on a task they've been fighting with. In some way, give any three people a moment of appreciation and/or hope - let them know they are noticed.
I don't hold to this as much anymore, my life has been particularly busy, but even when I started I asked myself "How much time does it take to make one comment to someone? Especially when a simple comment/compliment can have such a strong and postive effect on them?" I think I'll revive that practice. Thanks for the reminder.
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One side note to the comment above about smiling at people, is what I do. I people watch a lot. Frequently I see people that look weighed down by thoughts and issues, so I give them a smile to try and brighten their day. Sometimes, I start to wonder who is people watching me, wondering why I'm so focused, so I laugh at myself and beam out a big smile to really make them wonder. Other times, I see people happy, and I share a smile in their direction as a way to congratulate their happiness and reinforce it. Hell, you'd think I'm a fool smilling all the time, which isn't the case, but it sure doesn't hurt to smile a little more each day, whatever the reason.