Think of your body as siblings not twins
You move differently with your left side than you will with the right side of your body. Being symmetrical does not mean that each side moves equally. This of your body as siblings not twins. Usually we have a stronger side and a more flexible side. This will allow you to move into a pose easily on say your left but have to work into the pose on the right. In many private classes we will work on one side with more balance (say Tree pose) to increase strength and the opposite side more poses that increase flexibility ( wide V/ wide legged forward fold).
This frustration might keep you from taking a yoga class. Once you have taken a class or two the balancing between left and right becomes second nature and "fixing" or moving into the position becomes easier.
This variance is not always just left to right but can be bilateral. Having strength in your left leg does not always mean that the left arms is stronger that the right. It is very common to have a left leg and right arm stronger that the right leg and left arm. This disparity comes from which leg you use to balance on while waiting in line for example. Or with arms which side you use to reach for and carry items.