It’s not actually ‘habit’ but ‘dead habits’ or superstitious beliefs and actions, as the poet has nothing to worry about the good human habits. Tagore has compared those old and useless habits to a dreary desert that can choke a river of fresh water. This metaphor is drawn while comparing the ‘reason’ or logical thinking to a clear stream. The superstitions and prejudices curb the progressive thoughts and make a nation stagnant. These are not at all relevant to the present situations, but people still like to cling to them. That is why the poet has called them ‘dead habits’.
Similar Question: What are reason and dead habits compared to and why?