I don't know if this is so bad, you represent an ace or king high flush and I highly doubt anyone who cant beat that is going to continue.
I would immediately toss AA, KK, QQ with no spade here.
I would also toss a few spades higher then your 8.

I wouldnt of done this myself, but It might not be a bad play at all. There are ton of hands that beat you that are going to fold. Also, youve done everything in your power to win this and now you can fold with 100% confidence that you are beat if theres anymore actino.