Athletes from amateur to professional level all experience muscle fatigue at some point. And if your goal is to quickly build muscle mass, this is something that you will run into sooner or later.
Keep in mind that when you are working out, you are slowly wearing down the muscles, tearing the individual muscle fibers, and burning all of the energy that your body has stored. All of these things contribute to fatigue.
One of the things you can do to build muscle mass quickly without running into this problem is to train the body to supply energy faster. Muscles receive energy in two different forms: aerobic and anaerobic metabolism. One is generated from oxygen and one is generated from energy stored in the muscles themselves.
Aerobic metabolism is slower, and therefore results in quick muscle fatigue unless anaerobic metabolism can kick in. The problem that most people have here is that their bodies are not trained or capable of storing large amounts of anaerobic fuel.
So what you must do is train the body to efficiently deliver larger amounts of oxygen to the body so as to increase quickly the amount of energy that the muscles have available to use. This reduces the risk of muscle fatigue and allows a workout to continue for much longer. However, it takes several weeks or even months to train the body to effectively speed the flow of oxygen enough to keep from experiencing muscle fatigue based solely from a supply of aerobic metabolism.
How you do this is the more difficult question. Your best bet is to consult an expert, either by checking out one of their products, or scheduling an appointment with a sports therapist.
They will help you devise an appropriate training method to help ensure that your muscles are as strong as possible and reduce the risk of having a problem with muscle fatigue.
In short, if you want to build muscle quickly, fatigue will be a concern. If not now, then soon. But it is something that can be minimized with further education and training.