I get into this rut as you mentioned. But to others it does not sound like you are in a Rut. We get to different levels of playing, Just go Day to Day and you will get through this. As mentioned take the song and learn a measure at a time. I have 50 plus and I still need to do this. Take your time, Where are you going?? Your playing should be an enjoyment, not something that frustrates you. Just play and enjoy your guitar. Getting with another guy always helps. I am a bed room guitar player now, but I still enjoy playing my guitar. When I wake up I usually start playing within the hour or so and I still love playing the guitar. I don't learn stuff every day. Matter of fact I am just fumbling through the finger board and not playing anything, but at least this keeps my fingers moving. Just go Day to Day, if you enjoy playing you will get through this. Your guitar should be your best friend. When you start thinking like this you will move forward