Set them too high - you'll be disappointed when you can't reach them and lose the motivation and drive!!
Set them too low - you won't be using all your potential and sell yourself short!
Look at your progress in the last few months, analyze it, if you're happy with what you've accomplished set your next month goals 10% higher; this way you challenge yourself and test your capabilities as the same time.
If you're not happy with what you've accomplish set your goals much higher to test your capabilities and then challenge yourself with the 10% increase each month.
Don't forget to improve your knowledge in the mean time, you won't be able to advance and reach the higher goals without proper training and hard work.
Set them too high - you'll be disappointed when you can't reach them and lose the motivation and drive!!
Set them too low - you won't be using all your potential and sell yourself short!
Look at your progress in the last few months, analyze it, if you're happy with what you've accomplished set your next month goals 10% higher; this way you challenge yourself and test your capabilities as the same time.