Take what you can from it. Good interviewers know bad interviewees, and that that doesnt always reflect on in job performance. They should take your CV, record and references into balance with it. I'm also terrible in interview, I've done 4, 3 of which were 8 years ago.
Make note of what didnt go well and change plan for next time. Thats what I did with interview 4, recently, which went badly (very badly as far as I'm concerned, I brainfarted on questions I should have just knocked out of the field). I also prepared for the wrong sort of interview, so a lesson for me was check what to expect beforehand; what sort of interview.
Past that its as much a numbers game as anything. If 10% of applications go to interview and youre chances of passing are 10%, do the maths on the applications you have to send out (hypothetical numbers, I dont think things are that grim, but that depends on job/field/background etc).
I have a couple of reasonable ideas of what I'd like to do (the interview I believe I've flunked was for something that was WAY top of my list, after that, dont know), but bear in mind its all a journey. You should look at any application as something that can lead to something else, not something that youre going to be stuck with. Any change can tell you something more about what it is youre actually after, even if that exact change isnt the one you want, and better than than just going through the same motions again and again (done that too, resigned to start production).
Also, dont take any of it personally. Try, learn, try, learn. You never know where that might lead you.
Edit: I realise this contradicts my avatar, but there is only try. The only possible way to give yourself no chance whatsoever at anything is to not try.
