Upper body relaxation is important. It might help to place the hand that stays on the bar as far away from the stem as possible. Try to relax the arms. The body tends to go where you look, so please don't look down when you grab the bottle, look at the horizon. To paraphrase Mark Twain, "buy rollers, you will not regret it if you live". Rollers will greatly advance your handling skills. (But it helps to have a sense of humor and a mattress!)