Good job on the fur, Sahra :] So you're aiming more on content than lineart?(No pun towards Lineart artists, I assure you) Lovely... Start training on shades and shadows, the best thing is to look at shadows, alot. Include alot of strong shadows, try to work on shades and gradiating between dark and light.
That's all I can tell you right now, send me a PM if there's anymore questions you need answered.
In accordance to relative stress: Don't get used to it, just relax, don't think too much about what others want to see. :]