I have a gravity bong for that.
I'm playing too quickly
My guess is that you are moving quickly to get away from the tension that you are feeling inside when you have to move. Breathe, relax your muscles, and tell yourself the slower you play, the better you will feel. In a good game, I can feel my heart-rate go up and learning to relax helps lower that a lot.
When you first log in, you could start by playing a warm up game against a bot. They move quickly so you don't have to wait for them, but there's no clock to pressure you and it's a bot so it doesn't care how long you take to make a move removing any concern that you're irritating your opponent by taking your time. Once you can get yourself into the frame of mind of working through the position before selecting your move, then take that mindset with you to your human games.
I know this sounds like a silly question... but I'm playing too quickly and not calculating enough. I know the simple answer is 'slow down and calculate' but for some reason I'm really struggling - my opponent plays a move and I feel like I need to respond instantly. Any tips for how to relax and what I should be looking for in calculations? Thanks.