There you have the answer play with more people and less on your own. Music and in particular your skills and knowledge need application and in a form that you cannot pre determine. When practising on your own you are using your own imagination to create and play, when playing with others you are not so you have to adapt. That means listening to what is happening, analyse it and come up with an answer in the blink of an eye.
Now the general story is that when playing in new situations the first few times are the best because that's when you get the most info to react to, so you play good or bad. it soes not matter which one good or bad it is because you will learn and adapt it in to the next situation. When this applies to a song in a jam situation, then the first few times all players are "ears on". Then as the all settle for what works "ears turn off" and so the spontaneity of the playing goes and it eventually becomes stale of boring. This is common at jam sessions the same songs and the same players doing what the can do[html] best, which is to play what the know.
This is where the influence of a teacher or another player comes in, they make you think different, so in fact that makes you approach your playing different. yes you can copy other players and learn styles but that is great for discipline and playing in bands, but it is not learning to improve musical skills as such, it is just collecting information to reproduce. To do this own your own you need to listen to diverse forms of music to what you know, appreciate how it works and see if any of it can be used by you in your playing. It is surprising the results and similarites other forms of music come up with when compares to what you know...after all it is the same notes and maybe just different time sigs, keys, tempos is enough to spark you thinking.
I was once told that a collection of flowers and plants does not make a good garden..it is a collection of flowers and plants. The same can be said for music and techniques, when put together they don't always make a good song. We all need the outside influence of others to help us see what can be.
