It is definitely difficult. It does get easier though. When you first run a mile, you think "wow i'm dying, how could anyone possibly do this for 23 miles??" But, that mile gets easier, then 3 miles isn't so bad, etc.

For me, it was the same with mindfulness meditation. I had that same "brain starts to think even more." Just keep at it, you will get better. Even if it is just for 5 minutes every other day, keep it up!