I do if an unexpected hill pops up and I haven't geared down, or I find out I haven't geared down enough while on the hill. Trick for me is to find the right balance in letting the legs do the work. Which for means leaning back a little and resisting the urge to lean to far forward. doing some "hoover" riding just over the saddle on the flats will help you get used to it. To low of gear will cause pedal slap, so find a gear that gives you some resistance before standing. I also shift my weight to the down stroke leg.