When I (or a friend) need a mood lifter, I get sunflowers. Those smiling "faces" greet us all with a a burst of joy every morning. You can grow perennial sunflowers that come back to your garden each year. My neighbors have some that grow to be 10 to 15 feet tall, a beautiful sight to watch each summer!
Don't forget the health benefits of sunflower seeds; a great source of vitamin E, a primary fat-soluble antioxidant that helps neutralize free radicals.