I take it that you pressed the SAS release button during a night flight and scared yourself? Well we all make mistakes and I am sure you won't do it again. Instructors can only teach so much and it is up to professional pilots to read the RFM and understand the location and function of switches and buttons and which ones not to play with (normally red ones).
I am amazed at the amount of AW139 pilots I see who will happily correct AP problems in flight at 150 kts by de-selecting and re-engaging AP's 1 and 2 with no verification and little thought to the consequences.
Next time you are in the sim ask the instructor to fail both AP's when you are flying at 150kts (preferably in IMC). You will have much more respect for those little buttons after that I guarantee.