Seche Vite help

Girlies, I need some help....

I bought a bottle of seche vite, have got about half way through the bottle and its now gone gloopy and more or less really sticky to the point where I can't get it to come out of the bottle!

Is there any way to rescue it? Is there anything I can put in it to thin it out and not waste my money?
If not is there anything I can do for future bottles to prevent this from happening altogether?

Any help would be appreciated muchly :)

Shel xx