Growing up, when we (one of my siblings or I) had convinced ourselves that a homework problem had stumped us, our father would do the following.
He would bring us to his desk, turn on the desk light, give us a blank sheet of paper, and sharpen our pencil. He would talk out the problem with us if we wanted and then (this part was key) would leave. He showed that he trusted us to solve our own problems.
And, surprise! We always figured it out.
I think often about that exercise, particularly when I feel momentarily stuck. What a gift to be given the habit of trying again, at a different angle, with a fresh piece of paper.