Be precise with your cleaning and sanitizing. That's one thing you don't want to mess with.
A few degrees in your mash here or there, not a big deal. Infecting it, big deal.
Agree 100% on sanitizing.
I ran into this advice for achieving precision. I apply it to all aspects of life, not just brewing.
1/ Measure with a micrometer
2/ Mark with chalk
3/ Cut with an axe
Ex fermentum, scientia.
Next time, preheat the mash tun with a gallon of boiling water, dump, add water at 162 and mash in. I was low on temperature on my first batch, but my second was spot on with the preheat of the mash tun.