Having too much to do and not enough time is one of the major causes of stress.
Often relaxation techniques can help with stress. These may include activities such as meditation or breathing exercises. However, relaxation is not getting to the cause of the problem.
To deal with the here and now of too much to do, using time management will help you. This tends to focus on planning your work and then working your plan. This is more about self management and ensuring that you are doing your priority tasks first, rather than being controlled by the tyranny of the urgent.
I write more about time management and how you can plan your work and work your plan at:
All the best