No it wasn't a mistake. I did this for my final cloud painting too, I make the whole thing digitally, because Photoshop is nigh-infinitely forgiving if you know what you're doing (which I do, w00t) then print it off and use that as a basis for the traditional painting I'll actually hand in. Basically I end up with two different finished works. The digital one SHOULD be less 'finished' than the physical one, but I often get carried away, so whether or not this approach adds or detracts from my final is yet to be discovered. I did two studies traditionally before, so the switch in medium shouldn't be too startling. Anyways, I'll be doing the real one tomorrow, for now you can see my digital study. Which I might add, you'll get to fully see, where as the finished 'real' painting won't entirely fit in the scanner.
If I can make something that looks like this in gouache, I will be very happy. If it looks better I might be ecstatic : D