I have answered this before but I don't remember where, so I will repeat myself.
I don't think we can "conquer" nerves. The thing that makes us afraid is a sort of demon, the collected manifestation of our self-doubts, feelings of unworthiness, fear of what others may think if we do badly, etc. . This stuff is insidious, it thrives on anger, self-doubt and our determination to subjugate them. The demon is very powerful. It thrives on any sort of emotion it can relate to, i.e. the ones I've just mentioned, and also if you're performing and you think, "gee this is going great!" and then splat you fall down. Because that very feeling of self-elation or patting yourself on the back is hubris, and it is a negative and false emotion. Up comes the demon. He's a sneaky one.
The only way to beat him is to welcome him in, sincerely invite him to make himself at home. "Coffee? Cigarette? Tea? Scones? Healthy vegetarian appetizer? Pop Tart? " You see if you fight him, he will thrive on that. If you make friends, he will get bored and go away, because he cannot accomplish anything with you. Accept that you are only human, and may make a mistake in this complex and difficult activity we call playing the piano for others. It's OK; will it matter if dolcejen or arensky or Cziffra or anyone screwed up in a piano performance in one thousand years? No, it will not. Will it matter (for us anyway, Cziffra has gone on) in a week? Maybe to us, but ONLY IF WE LET IT. This is the demon.
Easier said than done, believe me I know. Sometimes (not always) I used to be terrified to go onstage, panic attacks, can't breathe, all that. But not recently. About four years ago, this was happening backstage, and I just said to myself, "well, this is part of the deal." The fear did not vanish, but the resignation and acceptance of it set in, so I walked out, sat down, and was kind of shaky for the first piece, but then settled in and actually felt comfortable, and played very well. Usually when I had been that frightened before, things did not go well. I still get NERVOUS, but I haven't been FRIGHTENED since that concert. The demon has been neutralized. Nervous is ok, in fact I think it's normal for many great performers. Fear is bad; it is a false emotion, there is nothing to really be afraid of. And it lets that demon in. So if you can accept the nerves, you will not be afraid of them.
And while you are playing, do not judge yourself or what is happening IN ANY WAY, good or bad. This interferes with the process of making music. You may feel emotion, but not to the point where you ARE the emotion; your job is to CONVEY the emotion, not wallow in it. Excessive emotion can let the demon in. Just be there, doing what you do, pulling the strings.
This may require practice, might not work out the first few times. But let the demon in, accept him. It's a paradox, but it's the only way he'll ever go away, IMO.