Your fingers are starting to form hard chucks of bark on them, not only that, but they're getting longer and starting to sprout willow leaves at the end of them. You try to take a step forward, but find your feet quite fastened to the ground below you.
You were so preoccupied with your hands that you failed to notice that your toes and heels have started grow and force their way deep into the grassy soil below your feet. You struggle at first, but as the bark crawls up your legs they form together, causing your clothes to disappear into your barky flesh.
Your arms force themselves up into the air where the growth of your fingers of berserk, sprouting additional branches all over. The bark that has been crawling up your legs has now reached your torso and you helplessly watch as it swells and grows. Soon it covers your head and you loose all senses save feeling.
You feel yourself growing deeper and deeper into the soil, and you feel your branches streach out into near infinity. After what seems like hours you stop growning, and your face pushes out to form a few knots in your trunk. You can see, hear and feel and smell, but can't talk.
The last of your transformation comes when you stop panicing and somehow manage to smile. You realize that being a willow tree is the ultimate happiness and look forward to helping other bipeds realize true happiness.