Have any of you made any rookie mistakes, that you're willing to admit to :P, like that before?
Yup!
Your review of this thread might prove reassuring:
http://www.pprune.org/private-flying...-mistakes.html
Obviously mistakes can very very not good, if it's the wrong mistake at the wrong time, so I never want to minimize the importance of aspiring to get it right and always do better. But, don't beat yourself up for using the wrong registration on the radio, or starting with the mixture lean ('done that during a checkout!), that's not going to injure anyone.
Concentrate on the really important things, like keeping the aircraft upright and flying fast enough, the engine running well with enough fuel aboard, then not bumping into other things. and the rest will fall into place. For every new type of plane you fly, there'll be a whole bunch more new mistakes to make. The more you fly, and use checklists, the more you will see a core structure and flow in cockpit procedure, and that core will become fairly engrained in your technique - that's good.
And then you'll fly a type with a reverse of procedure, and the mistake will happen. After a half hour of checkout in a marvelous two seat tandom taildragger with a turbine engine, last summer, I was declared fine to fly it, and set about the required flight testing this month (with no flying in it the interim). I got a number of good flights in, and was feeling pretty good about flying it. The other day during a start, it suddenly gently went poof, and spooled down to a stop. Oops, I'd forgotten to turn the fuel on! (this type requires the fuel be turned off, right after ever shut down - I had got that right! just missed the checklist item to turn it back on for the start!). I felt silly, but no harm done. Reset everything, wait the starter cycle time, check the voltage and start again properly. Sure enough, I was back seat to my original check pilot two days ago, to check him out on the modification, and while using the start checklist, he managed to do the same thing! I did not feel so silly any more.
They're not really rookie mistakes, just keep them from being serious, or costly ones, and we'll all be able to admit we've done the same types of things!