Jeff,

THe best thing you could do in my opinion is to only use the sheet music as a reference to learn new material. Find compatible musicians to jam with and keep doing that. Music is never meant to be played solo all the time. It's like playing in a vacuum. Making music with others will help you grow as a musician fastest. You might bridge this gap by starting in playing in a mandolin orchestra if you can find one in your area. (This still keeps you on the printed page however). It would be a transition to jamming and learning to improvise. You can learn to improvise but the only way to really do it is to take a chance and put yourself in that environment. Make plenty of mistakes and learn which means you have to choose your musical environment carefully. Play only in supportive situations.

Frank Hamilton