I feel your problem, I had the same problems for a while, but not any longer.
I got a tip from a german player that worked for me, but it's not a miraclesolution.
But its a bit of mind play, have 4 darts to throw, but only throw 3 of them, so that you always have a dart in the dog hand.
In that way you are implying to your mind that you arent throwing the last dart, and then you practice to get all three darts in the board where you want.
And even after you return to only playing with three darts, you have a ghost dart in your hand that your mind makes up.
As I said, I may not work for anyone, but that made my last dart-tension drop, and now I dont even think about the last dart.
After all, darts are almost only about the mental side of the game, if your technique are good then the only thing to work with are your head
I hope that this tip works for you, and I hope you will be able to kick your inner demon out
And I hope you will hit your first 180 soon
Its a good buzz and its good to break the ice, then the 180s will come flying
Cheers!