If everything was perfect, there would be nothing left to do. If you had already achieved and become everything you ever wanted, there would be nothing left for you to look forward to experiencing.
Thankfully, things are not perfect, the goals have not all been reached. There is always room for improvement, and always some enticing possibility to beckon you forward.
The problems, the imperfections, the challenges and setbacks make for a very real, very positive possibility. It is that life can always get better and better.
When you've worked with persistence and commitment, and have finally reached the goal, what's the next thing you want to do? You want to put all that hard-earned experience to work again as quickly as possible on an even bigger goal.
Achievement would indeed be empty if it meant that you could never achieve again. What a blessing it is that there's always more to be done.
Life is best when you're busy working on it. And it can just keep getting better and better.