And the first 80% are usually the easiest.
Well, not necessarily easy, but easier.
It's the classic 80/20 rule.
And it applies to pretty much everything in life.
It even applies to leaning a new language.
When you learn a new language the first 80% are relatively easy compared to the last 20% that are necessary for complete mastery.
Most people will never reach 100% in their second, third or fourth language.
Just like most people will never really master anything.
Simply because the last 20% are so hard that it's almost impossible to achieve.
Not impossible but it would require complete immersion in the subject and doing nothing else for a really long time.
Time that most of us just don't have....
So either you go for the 100% or you don't.
And if you don't, then don't beat yourself up if you're stagnating and not getting any closer...