Just sit down and fill up a document with "next time I would do Y instead of X". You can also explain why, or what experience inspired the lesson. But definitely write them down. Keep the document handy. Over the next few months you'll keep having retroactive facepalm moments; you might as well get something out of them.

Right now it feels like you will never forget the whole crazy ride. But next time or the time after you'll read through a lessons-learned document and be very glad you have it.