Tiredness/Fatigue: This is quite common after a major operation. The body is busy doing the repairing process of the wound.
Heart is getting accustomed to the changed scenario. Allow adequate rest for the body and mind. Engage yourself in light recreations like reading and listening to music. Take a short (half an hour) afternoon nap. Watching TV excessively is not good as eye strain may cause exhaustion. As the days progress, you will feel better.