The nature of the mind is such that it becomes that which it intensely thinks of. Thus if you think of the vices and defects of another person, your mind will be charged with these vices and defects at least for the time being.
The person who knows this psychological law will never indulge in censuring others or in finding fault in the conduct of others. One will see only the good in others and will always praise others. This practice enables one to grow in concentration, yoga and spirituality.