I would definitely do what the following have said. It is not only important to input the notes but to actually automate them to where you are somewhat forcing them to sound realistic. And not only is it important to automate the instruments themselves but to automate the space and effects along with the music to give the piece more of a shape. Maybe your Violin patch needs expression and modulation for more dynamics? Need to change to staccato with MIDI data, use key switching! Got a Flute patch, let's add breath automation data to give it more of a realistic sound... etc. I'm not an expert, although I am currently in the process of absorbing mixing and automation techniques, however we will forever be students so don't limit your knowledge and say that you are complete! There is so much to learn even for the experts out there, so for a random word of encouragement, don't give up and keep experiencing new ways to input your knowledge to learn more along the way! Also, don't be afraid to play around and Practice these skills... it's not only a matter of what you know but application is a must.