Why would a 1RM (maximum strength) change everyday ?

In example if I start with a 1RM of 200kg and train with 95%, 190kg, I'll progressively add weight to stay around 95%. Week 1 I may lift 190kg, Week 2 192kg, Week 3 194kg and so on. I increase the weight as I get stronger. I don't exactly know how much I can gain per week/month but my increments are adjusted when I test again my 1RM. It's always better to add weight too slowly rather than too quickly. I often overtrained when I wanted to add weight fast to create the illusion of a progression.

In 2-3 months if my training continues like that I'll have made major progress. I hope this time progression won't stop.