And sometimes even if you are an expert, you may still make a mistake if you aren't in an optimal frame of mind - for example, if you didn't sleep or eat proper

And sometimes even if you are an expert, you may still make a mistake if you aren't in an optimal frame of mind - for example, if you didn't sleep or eat properly or had an altercation with someone, or your normal routine got messed up ... sometimes it is just that - a shitty day in your life with nothing to learn but to just go through it.