Whoever gives up an action simply because it is painful, or out of fear of bodily strain, performs a renunciation of the passionate (rajasic) kind, and does not gain the fruit that true renunciation brings.
Explanation
Krishna is explaining to Arjuna the three kinds of renunciation (tyāga), following the tamasic kind in the previous verse. Here he describes the rajasic (passion-driven, restless) kind: dropping a duty because it is hard or tiring, not because of any real insight. Such giving up is driven by comfort and fear, so it does not bring the freedom and peace that true renunciation is meant to give.