If honestly at 50% there is something to strive for, what to achieve. A person should always improve. If we do not work on ourselves, then we will not achieve anything
In my own opinion you're right because its hard to get a 100% happiness, but for me if you love what you do and you're satisfied of what you have happiness will just follow.
You both nailed it. Once you are opportuned to be doing what you like. No matter the obstacles, you will be contended.