One of the things about gardening are the surprises, some good, some bad. I've had this little frog that holds water in the same spot for several years. When I planted the double impatiens they were small. As they grew, the flowers hung over the edges of the container and would fall off into the water held by the frog.
Sometimes it can be something as simple as putting a bench somewhere in the fall and then realizing fragrant lily of the valley sprouting up under it. One time I planted anemones late in the fall forgetting that the hosta would come up int he spring. I had these little red flowers pop up in the summer over the green foliage, it looked great. That's the perfect mistake, and they happen all the time in my garden. Don't be afraid......to experiment with color combinations and plant selections, you never know when things will just work. We all make mistakes, but in the garden that can be a good thing.