I just think of my favorite songs and "air play" them in my head.
Tigergirl, many an experienced rider has said that when you are not the least bit nervous to ride, it's time to park the bike forever. A bit of nervousness is good because it keeps you cautious, so don't get too complacent. Even very experienced riders have had bad crashes. I say this because you said you just want to go with the flow. Nothing wrong with concentrating on what you are doing. When working the controls become 2nd nature, then you will naturally be able to concentrate less. This only comes with seat time, unless you can visualize riding while you are not on your bike. We can all always improve and it's wise to critique yourself, such as, "I forgot to check my mirrors or check on-coming traffic in that intersection, need to do that more! or Oops, took that turn a little too wide," etc., it only takes ONE unlucky miss!
As for group riding, I did that a lot in my early days. Different groups ride differently, so it's important to ask questions about the group's riding style. For beginners, yes, newbie-friendly groups are important. In a small group, there should be at least one rider who is very experienced, and you should always have a meeting to discuss and agree upon your group "rules", for everyone's safety. Others can be very inspirational and confidence-building, as you see how they ride, that can show you what your own bike can do as well, such as, how they handle curves and uneven/tricky surfaces, things you may not attempt if you were alone. You see that they don't fall, you get the confidence that neither will you.