You got it.

[Billy does just that, resetting the timer to zero before furrowing his brows and thinking for moment. He'd had lots of time to consider Loki's technique while he was waiting, but... hmm.]

I wonder if you're actually focusing too hard. If you tense up too much, the energy won't flow through your body properly, and if you can't get your energy moving then the magic won't move, either.