As you said some people work hard to achieve their goals but still don't achieve what they want. Here what I feel is hard work alone will not help in achieving. Hard work along with smart work is required. A proper planning should be done to achieve various thing and then work hard according to the plan.
For example, a student will set a target to score 90 marks in the examination but a proper planning won't be done. A student will work hard, byhearting things, work day and night but end moment he won't get result as expected because there would be no proper planning of things to be done and completed. I am the own example of being such student.
So hard work along with smart work is necessary to achieve something in life.