I agree with every word of advice given above. The "jitters" should never entirely leave you, for if they do you should give up flying. I fly helicopters for my livelihood and light aeroplanes for my recreation and after more than 40 years since I started, I still have slight "butterflies in the stomach".
This feeling is stronger when driving to the airfield or workplace, but largely disappears once I'm airborne. It's good advice to know the workings of your aircraft well, to do a thorough pre-flight, to be mentally well-rehearsed for the possibility of engine failure and other failures, to fly very defensively as outlined by someone above.
Read about other people's flying experiences, talk to experienced pilots and always fly as though you have your nearest and dearest as passengers. Fly regularly so as to avoid long periods during which apprehension might build up.
Remember that you are in a helicopter which gives you more scope to land in a hurry than is possible in a light aeroplane, so if you practice full autos periodically with an instructor your confidence should grow.