Really, totally without thoughts? Usually it is very difficult, nearly impossible, for someone to shut off all thoughts until they are very advanced at meditation. Remember any thought counts, even "Hey I've not thought for a while."
We're so used to having thoughts constantly barraging us that it can take a while to shut them off totally. But that doesn't mean you are failing. I would say there is no failing, as long as you constantly bring your attention back to that which you are focusing on.
There is a course
on another site that suggests using the mantra "I am." I don't know how well it works, but I imagine as well as any. I've been trying to use it.
Just meditate, and don't worry about results, expectations, or anything. Even if it goes really well one day, it may not the next. It doesn't matter. Make it part of your daily routine.