You should always play musically especially when you are alone in your practice room. This is the place where you can really let yourself go and try things. No one will hear you so go for it! You will be able to play musically in concert only if you practice this way. If you never take any risk in your practice room, will you take some in concert? Most likely not. So don't wait for a miracle; make it happen right now and you'll be able to do in in a performance.
I am associate principal horn of the Singapore Symphony Orchestra and the author of the progressive methods. I'm happy to share my experience as a horn player and teacher with you.