tension is the biggest hinderance to learning to fly, and unless you can recognise it and relax it will be with you for a lot longer than the first few hours. Believe me , I teach quite advanced pilots and I regularly have to make them relax, you should see the difference in their flying once they do. There is no need to grip the column like you are afraid somebody is going to take it away from you, in fact your instructor is more likely to relieve you of the burden if you do.
The same goes for your legs on the rudder bar, When I did my basic training I could not understand why my legs ached so much at the end of each day. Its amazing I didnot damage the aircraft.
Relax and enjoy it, it costs too much to get stressed out about.