Life's Muse's
I've now spent more than 5 years practicing photography, and in that time I have thought about quitting more than once, only to be encouraged and have my passion for the art and skill of photography rejuvenated, by loved ones, admirers, life event, or even just new perspective.
There will be many times you give up, and just as many re-attempts. You will have bad photoshoots and even worse client attitudes, there will be odd days, but there will be many better.
There is always tomorrow. There is always the next shot.
but that doesn't mean the opportunity will always be there...
The most common lesson I've learned among all of my experience in life thus far is that everything is finite. Take the time to be prepared, practice, keep your eyes sharp. You never know when a chance will arise, or how quickly it will go.
Make sure you seize it.