I would call Jason Bourne to come help me out
psychological:
I dont quite know if your guitar/hobby would be all that important, simply b/c working out and heavy physical actions lead to neutralizing stress hormons. So, as long as you keep moving, you would stay sane i think. Thats why Id recommend doing pushups/pullups/jogging instead of playing guitar
You will have to get used to seeing ppl die, maybe even loved ones (and still not loose focus), so you want to be psychological tough already. I think theres many ppl that cant even deal with that during the first weeks so youll have a huge advantage if you can keep that focus in any given situation.
Also, what I think could be essential, is knowledge of military tactics, so that you always think about the risks when looking for a place to sleep, seeing a group of ppl somewhere, etc. You will want to be aware immediately of whether other ppl are armed, where you could escape, what places/regions are more dangerous than others simply b/c of their geography etc. Being aware of those things and making decisions based on such thoughts might be the key to survival.
physical:
I really like the above notes, except for ALGs dog. The problem Im having with that is that the dog wants to eat, and food will be scarce. Also, the dog is a source of uncontrolled noise (if hes like most dogs). That might be dangerous for me and him.
Another problem is that of emotional attachment. Maybe my scenario is a bit too negative, but I assume that Ill have to fight for my life and I cant take care of a dog in that situation.
Aside from having good shoes and clothing a good backpack is essential. Also, having some kind of tent or a big canvas to keep you and your stuff dry. Preferrably camouflage, so that you can keep yourself from being seen.
the ability to build traps might be essential. Assuming the worst scenario that includes atomic fallout and death of most plants and animals, it might be necessary to take other sources of food into consideration

and traps will help you with that lol I dont wanna write it b/c it feels so sick!!
The ability to read tracks is essential too, b/c you want to know who else is around.
Anyway, maybe Im wrong and all ppl will cooperate a lot more and everyone will help building a peaceful new world.
A good book I read that feels quite realistic is Pulse by Stephen King. Great book, really draws you in. Even tho ppl there have to deal with the fact, that almost everybody else is a zombie whose actions are controlled to a certain degree by some kind of flock-consciousness...