Lucky you!
It's 12 miles each way so I hard task ahead.
some times I'm absolutely nackered by afternoon tea break.
My first suggestion is to knock the negative thinking on the head.
Yes, there will be more physical demands on your body, but they will be different and, most likely, your body will adjust.
However, there will be a mental side to things too. Cycling to work (longer than yours) had me arriving early and in great form and ready to tackle anything. The ride home was great for clearing the head and leaving any stress behind - a great way to prepare for the free hours.
I went slowly, slowly. First one day a week, then 3 then eventually up to 5.
I investigated routes to find the "best" one. The "best" was rarely the fastest. Especially on the way home.
https://cycle.travel/map is my favourite.
If it's a new bike I'd suggest getting familiar with it so you're confident dealing with any issues.
If commuting in the dark then good lights are a good idea.
Commuting was the only time I bought "proper" cycling clothes - a jacket & rain pants.
The only time I didn't enjoy commuting was when I got a gps unit and started "racing" myself.
Best of luck - commuting by bike can be great!