I had the same white knuckle issues in a C150 originally - I think I was paranoid the plane would flip over or veer off, so I was continually over controlling and gripping as if my life depended on it.
My instructor at the time took me up on a fairly bouncy day and just let it fly itself - largest turbulent upset was around 20 degrees roll, with just a small correction needed.
He then flew a virtually perfect circuit and right down to the flare "hands-off" - very impressive, and an excellent lesson in trim and rudder control.
The more you grip, the bouncier it gets - so if you're in anyway nervous about chop you should just relax and try and let go (which is exactly the opposite of what your brain thinks you should do).
Just another one of those things you need to learn by practice/experience.