A very common idea when learning to sharpen is to use a really cheap knife in case of mistakes. A lot of people learning to sharpen say that they just can't quite get a good edge. There is a lot of reasons for this but one may be the knife itself. The steel in a very cheap knife is intrinsically incapable of being sharpened to a really good edge.
When learning to sharpen it is better to choose a good knife. Take care when sharpening, stick to 1000 grit or higher and move carefully and it is very unlikely that you will do any severe damage that cannot be repaired. You will likely find a much better result when sharpening.