Wasn't going to chime in because I wasn't overly successful, I didn't start wrestling until 10th grade and took quite a few beatings. The more I think about it, maybe that perspective has some value.
1. Don't ever give up. You're going to lose, especially as a newcomer. Everyone starts some where. Don't worry about it, just keep working. In practice, in matches, in the off season. Kids that don't wrestle might run their mouths at school, doesn't matter. They aren't gutting it out like you are in that room and they'd get their asses handed to them too, if they had the balls to try. You can't get experience by watching from the bleachers. Losing matches doesn't make you a loser, quitting does. It is far worse than losing, so just keep working at it and success will come.
2. Don't be timid. Don't worry about doing stuff wrong, screwing up, looking foolish, etc. It happens to the best, it'll happen to the new kids. Being timid isn't going to keep you from getting hurt or from making mistakes or keep you from losing. It'll only hinder your growth. F it, let it fly.
3. There is no substitution for experience and that takes time. You know what doesn't, comparatively? Strength and conditioning. Build your endurance, lift weights. Eat a little smarter but don't cut weight. You probably won't be a great wrestler right out of the gate. You can have a good gas tank and get stronger and that will help to equal some things out and keep you in some matches. You don't need wrestling knowledge/experience to do this.
4. Wrestling is probably the toughest sport both physically and mentally you'll ever compete in for lots of reasons. Hardest practices, always something hurt (not injured), no teammates to bail you out, mistakes on display, constantly getting humbled, losses much harder to deal with. However, that feeling from getting your hand raised the first time after giving everything you have from start to finish, legs shaking, arms burning, hands stuck in a grip, sucking air, is unparalleled. The feeling of accomplishment is unlike any win in a team sport and you'll never forget it. It makes everything you've gone through well past worth it.
Others have hit on the finer points here with technique and starting small but the above seemed important as an outclassed new guy on the mat who started too late.