Well, part of life and work is being able to deal with stressful situations gracefully and with a clear head. So, I don't fully agree for example that you would have done well at Google if you could not run the gauntlet of their interview process.

A big part of the issue is most likely that you are making the interview and job opportunity to be a more significant thing than it really is in the grand scheme of things. Don't approach it with a completely careless attitude, but go in looking at it more like a casual first date where you are BOTH getting to know each other equally.

If you don't know something specifically, then say so, maybe describe how you would find the answer in real life. Be aware if you rely too much on "crutches", maybe you need to reassess your skills if you can't write 100 lines of code without finding half the answers on Google (just generalizing here).