I used to think that too about the missing a day or two not being an issue, but your blood pressure will go up if you miss a day.
If you don't do anything physical you won't notice the rise in BP but it will rise. (remember it's called the silent killer because symptoms go largely unnoticed)
Motocross will raise your BP anyway, so when you combine that with the uptick from missing meds and you're playing with fire so to speak.
I take a diuretic as well, and know it can be a hassle to have to pee so often. The good thing is that once the race starts your adrenaline will make you forget that you have to pee if your timing gets off. lol