I'm just like you, my stutter is a complete rollercoaster, it changes all the time at work and sometimes I can't even speak to my gf at home when I'm overthinking it. All I'd really focus on mate is just being really kind to yourself when having a bad day, as having a bad day will cause a drop in your mood and this can usually worsen your fluency, leading to a vicious circle. Focus on times when you spoke well and when you have negative thoughts about your speech just delete them in your head, i.e think of something else. I know the frustration, sometimes if I try not to think about it it can still happen, but just remember that overthinking or beating yourself up will never ever be beneficial.