In Aikido training, as with many aspects of life. people often impose self limitations that inhibit their growth. This frequently happens without their even realizing it. A caring instructor or sempai will help this type of student break down these self-imposed roadblocks to help that student achieve things they never thought possible. These roadblocks can often times be more that just the fear of performing a physical technique. They can also manifest themselves in both the mind and spirit of an individual, and affect their view or perception of Aikido, and life off the mat as well. Identifying these self imposed, growth limiting roadblocks, and helping that individual work through them in a safe, positive manner, is the sign of a true sensei.
Looking back on my youth, I always admire and respect the teachers I had then, who at the time, seemed the toughest and pushed me the hardest, making me do things I didn't think possible.
Or, I could be totally full of beans.