It does get tiring after a while. It's almost like you have to disconnect from the pleasure of eating during the time of the Master-Cleanse and reconnect afterward. I remember feeling the way you did on my first Master-Cleanse (went for 12 days) but I managed to do a 21-day Master-Cleanse this year, so keep trying. I think any length of cleanse is great (10 days plus, that is) but it is good to experiment.