Regarding forgetting things
I only routinely take two things onto the boat, my mesh backpack with all my scuba gear in it and a regular backpack with everything else in it. Years ago, I started packing and unpacking both of these in the same way/order each time. That habit has made it very difficult for me to forget something important at home before the dives or on the boat before heading home. The only common item that does not fit in my backpack is my boat coat. I take the boat coat on many dives, even when it may be unlikely that I will need it. I have forgotten that I had it with me a couple of times when it was warm and sunny and left it on the boat. I have my name and mobile phone number prominently written in Sharpie on the neck label. The few times I have left it, I have gotten a call from the crew before I was far away.
I deal with assembling my dive gear on the boat in the same way. I do it in the same way each time. It's been a very long time that I have jumped into the water without my gas being on or without weights in my pockets