Why can't I get my arduino to remember my sketch!!!

Hey everyone!..I’m very new to all this so sorry but you will have to bear with me!
So I’ve just got my arduino and I’m using it to control a servo, after I write a sketch and download it the servo carries out the program but I can’t get it to remember it as in the morning it’s gone!..please what am I doing wrong!?..replies in basic English would be much appreciated …

I suspect a programming error in your sketch or a hardware error in your Arduino. Please post your sketch and tell us what model Arduino you are using.

Hey john thanks for replying ..I'm using an arduino uno and downloading the sketches from the examples in the library just to start eg sweep...as I've said I'm very new to all this or can't this be done?
I've also tried writing a new sketch based or these examples they download fine and move the servo ..it's just that in the morning to board hasn't remember them..sorry if I'm being a dimwit...cheers

What does the board do the next morning that makes you think the sketch is gone?
What happens if you disconnect power to the board for only a short time?
If the sketch is uploaded and runs fine, it is definitely stored inside the chip and can not easily "be gone"

Hey guys…I’m soooooooo sorry but as I said I’m new to all this and I’ve been writing a different sketch for different pins instead of one sketch to control the different pins!!!..I did warn you I’m a dim wit!!

Thanks for everything…Brett