I can do 60 words a minute but still can't get that 40 WPM with %100 percent accuracy

same here, I have great difficulty to get my accuracy nailed down.

But the good point is the more accurate I am the more fast I am.

At the moment my average accuracy is at 94% at 40wpm but when I reach the 98% even if I seems to slow down I reach 50.

The real challenge is to be accurate and fluid, so you don't stop to think about the next key. That's what really slow you down imho.

Just focus and don't try to be perfect. Don't focus on the words that are next to the point where you mess up.