No matter what shape you're in, you won't be "fighting shape" until you've actually been sparring. There's a big learning curve that you overcome through sparring i.e. getting over your nerves, learning how to relax while under pressure, and carrying out what you've been training.

The actual boxing training is better performed in a gym with someone competent instructing you. I found out for myself that the bag work that I did at home prior to going to the gym did nothing to prepare me for the demands of the sport.