What limits your happiness when you only have an achievement mindset is the assumption that you are not complete unless you achieve something. This causes you to view yourself as incomplete much of the time which causes you to feel less than completely fulfilled.
What limits your happiness when you only have a present moment awareness mindset is the realization that you are complete already regardless of whether you achieve anything or not. This can cause you to view yourself as so complete that you don’t need to take full responsibility for all the stuff that happens in your life, which causes you to feel less than completely fulfilled.
The solution is to find a perfect balance between the two mindsets that gives you all the benefits of both with none of the disadvantages.
Here's my best take on this to date: