Every business goes through highs and lows and sometimes you do need to completely change your marketing strategy, but that's all part of being in business. If photography for you is just a job, then quitting and doing something different might be exactly what you need to do in order to be happy.
What I hate most is hearing about somebody giving up their dream to be a professional photographer. There's a big difference between walking away from a job and giving up your dream. I found this quote from Bob Parsons of Digital Entrepreneur.
There's an old Chinese saying that I just love, and I believe it is so true.
It goes like this:
"The temptation to quit will be greatest just before you are about to succeed."
There isn't a single artist in our industry who at some point in their career hasn't questioned their direction. Remember, you're not alone, because we've all been there.
Never let go of your dreams!