Nice work! Running out of page is a common problem! Before you start drawing, take a moment to first estimate the height and width of what you're planning to draw on the page. Stan calls this "drawing the envelope," and gets you thinking of where you want to place the drawing on the page. Give yourself a enough breathing room around your envelope to expand your drawing if you need to change proportions or just to have a pleasing amount of room around your composition. Take a look at the Basics Demo - Simplify Portrait from Observation, specifically the lay in. Right when Stan starts the drawing he marks off an estimate of the top, bottom and sides before getting to the big shapes of the head. Remember, these are estimates, and can change while the drawing, but should serve as the first proportional measurements you make on the page. Keep on drawing, and have fun!