We all grew up being told not to quit. It seems like the right thing to say to a person who wants to achieve. Many times it's correct to tell someone not to quit. If you're going to accomplish anything that matters it's going to come with it's share of challenges and quitting will do you a disservice.
However, sometimes quitting is the right thing to do. It may be that you're just not cut out for that type of work. Or, you're engaging in the wrong strategy in which case you should quit on the strategy but not quit on the work.
So should you quit or not? I think this is more of a gut decision than a logical one. Do you feel compelled to the work? Does it excite you? Is it really important to you? Or is it just something you're doing for the moment but don't want to look like a quitter to everyone else if you decided too? That's for you to answer.
The sooner you decide to either commit to the work or quit what you're doing and find what you need to commit to the sooner you'll be faced with more challenges that will likely cause you to question rather or not you should quit. Basically, it's always hard rather you're passionate about it or not. The difference will be rather or not you believe quitting is an option. If it's really what you should be doing then quitting simply won't be part of the equation.