The most difficult thing in Karma Yoga is to be in contact, in relationship with people, without forgetting that I am not serving another person but myself. In the initial stages, this involves making sure my own being, me, is whole, and later realizing that he and I are different parts of the same organism.
Karma Yoga is very difficult. It is real yoga and needs terrible vigilance all the time. I note that I am calm, peaceful, without jealousy. Very good. But can I live in relation with others all the time, and yet be inwardly watchful always?
It requires tremendous effort. Yet, so long as it needs the effort, please remember that it is still not you. You are not examining yourself, but examining a reflection, a shadow. When learning to drive, you need much effort, but when experienced, you drive in your sleep.
As long as self-observation demands effort, it is good to be careful. The moment you let go, there will be a crash.