Keep your expectations of your drawing ability realistic.  It will never ever be a perfect drawing.  Make it fun, learn something from each drawing that you complete, and take that with you to the next piece of art that you create.  You will improve over time, and that is what you should expect from yourself!  Perfectionism leads to frustration. 

One way to save.......

When your colored pencil is too small to comfortably hold or too short to sharpen, purchase a new pencil of the same color,  sand the flat unsharpened end of the old pencil and one end of the new one.  Then place a drop of wood glue on the sanded ends and join them.    Place tape around them overnight, then remove tape the following day.    Sharpen the pencil on the end with the old short pencil.    There will be no waste at all this way.