When you improvise, you have to really feel what you are playing. There are guidelines but these really are just that, guidelines! You can bend them and play with them freely because you are feeling what you are playing and because there isn’t much time to think, it becomes instinctive and you stop having to think as you listen to others around you. Once you start to do this you can add your own personal touches, and once you reach that stage, you can start to enjoy yourself more!