Saturn transit over Ascendant is never good. As per Kaalpursh Kundali , lagan or Ascendant is the head and when Saturn the planet of obstacles, delays is there on the head, the native can get depressed, lazy, concentration problems, cannot focus. Remedies of Saturn should be done to avoid malefic influence of Saturn.
Let me explain to you with an example. Say if Saturn is in Libra and in the Nakshatra of Rahu. Saturn is exalted in Libra, still it may not give the best results as it would be transiting in the Nakshatra of Rahu. Therefore till the time Saturn transit is from 6 degree 40 min to 20 degrees in swati nakshatra, Saturn will not be able to give good results, despite being exalted.