Sailboats often can’t go directly toward their goal. The physics of sailing dictates that boats can sail a minimum of 35 or 40 degrees away from the wind direction without losing too much speed. So if your goal is directly upwind (i.e., in the direction the wind is coming from), you can’t head right at it. Instead, you sail in one direction, gaining some ground on your goal, and then you tack (change which side of the boat the wind is coming across) and gain some ground while going in a different direction. Eventually, with enough tacking, you’ll reach your goal in a zigzag manner.
Isn’t it the case that we can’t aim directly for our goals in life, either? We can aim for something close, but maybe not at it. But if we gain speed, and have a number of attainable intermediate goals that take us in different directions (but always forward), we do at last have the chance to achieve our goals.