“One gets tired of Japa for two reasons. Sometimes one’s brain is fatigued, sometimes it is the result of idleness. If the former, then one should give up Japa for the time being. . . But if the latter, your mind should be forced to continue.” — Swami Vivekananda
Japa is the meditative repetition of a mantra or a divine name, like the Aum chant. One can lose focus during this kriyā (activity), either because they are tired or because they do it mindlessly. The result? A loss of interest and feeling bored.
When you’re exhausted, it’s better to take a break rather than chanting for the sake of ticking a box. But when you are doing it mindlessly, it’s often because you’re going through the process robotically.
During such times, try to master one part of the kriyā. Get the pronunciation of the specific word or yoga pose right. Focus on your breathing. Repeat the process for the next part of the activity. Try to stay focused for a few seconds at first. Then gradually extend the duration.
This applies to the practice of anything, mental or physical. If you feel tired, take a break. But if you are feeling bored (especially in the early stages of learning), break the activity down into smaller ones and try to master each of them.
Train your mind to become conscious by involving it in every task.