When you meet a real, sincere karma yogi, who is plodding in the line for six or seven years, you can at once feel his purity, his selflessness, his inner joy, his inner peace, his inner strength, his inner spiritual growth. You can feel his nearness to God. You can see occasional flashes or glimpses of divine light during satvic moments. He has a pleasant feeling of having justified the divine command in the grand plan or scheme of things.
People do not want to remove mala (impurity) by selfless service. They do not want to remove vikshepa (mental distraction) by upasana (worshipful contemplation). They think that service and bhakti are nothing. They at once jump to open the kundalini (the inner spiritual power) and raise the brahmakara vritti (the notion that only Brahman is real). They will only break their own legs. Rather serve and worship. Jnana and yoga will come by themselves. Kundalini will be awakened by itself.
In the neophytes, in the path of karma yoga, the idea of being a separate worker, the idea of agency, may be strong. You feel that you are doing all the works. However, in course of time, when the heart becomes purer and purer, you will actually feel that some higher power, God, is working through you. You will feel that your body and mind are only instruments in his hands.
"When thou doest alms, let not thy left hand know what thy right hand doeth". (St. Matt. VI - 3). Begging without any selfish motive, is not begging at all. It is pure yoga. It is for spiritual upliftment only. Remember - you cannot deny pain, you cannot wipe away all the pain in the world - but you can rise above pain by recognising your self.