Perhaps intentionally going back into the past is so painful that the subconscious mind will not allow it. It's really pretty amazing how your mind will make your body do anything it can to protect you, even if it is destroying you. Your subconscious mind is protecting you....or at least it thinks it is... getting you ready to fight, or flee or freeze so that you never move forward. This protective role of the subconscious mind is so powerful. I have seen a clients body jolt out of a light hypnotic state, so as not to deal with the past.
But getting to the root of the problem is an effective way to clear the past and move forward into the future. Perhaps you are not even aware (consciously) of what your limiting belief or the root issue is. Making a change, when you don't know or understand the problem is extremely difficult in a conscious state.