You cram because you don't enjoy studying very much. In the beginning, it's easy to procrastinate or avoid studying, because the threat of failure is distant. Later, it gets harder and harder to ignore, so that the short-term pain of failure overwhelms your short-term dislike of studying. Here are some tips:
Study A Bit Each Day.
Plan Study Sessions In Advance.
Follow A Schedule.
Find Your Child's Best Study Time.
Prioritize School Work.
Space Out Study Sessions.
Study Material In Chunks.