My experience (not some months) is that this is more likely to happen when your aura is particularly dirty. Of course, when it comes to mental focus and concentration, a huge role is played by your mental faculties, which are developed through practice and experience and as you can read on the JOS site about this topic, the "natural" power of your mental focus is visible in your natal chart, but it is not a genetic gift, it is the genetic result from previous efforts and advancement accomplished in your past lives. So, you cannot escape the part where you practice your focus, through void meditation and other techniques. This also comes naturally with meditations.
So, of course you have to practice your mind focus, but also be very consistent in your purification efforts.