My mother told me she used to get so frustrated when she would run out of bobbin thread.
She decided to time how long it took to replace a bobbin--it was under 30 seconds.
She figured 30 seconds was nothing to get upset about, and from then on, when a bobbin would run out, she would tell herself, "It is just 30 seconds" and carry on.
She would always wind 3 or 4 bobbins at a time so there was one ready to go. When she saw there was just one bobbin in the queue, she would watch for a good stopping time and wind up 3 or 4 more--never caught with an empty bobbin.