Leaving your food at ground level at night is taking a risk that it will not be there by morning. Many popular back country areas have a pulley system to enable hikers to hang their food well out of reach of bears and other wildlife.
The reasons we need to protect our food are also to protect ourselves and the bears.
Bears are naturally curious creatures who will not hesitate to shred your tent during the night if they can smell that candy wrapper or sweet drink you've kept with you in your tent. Do not take any food into your tent. Especially at night.
Bears are curious and have an excellent sense of smell. Tempting them with food left out at night is taking a risk. Not only does it risk yourself, your food and your gear but it also creates an unhealthy situation for the bear-human relationship. I think it's safe to say that keeping a fair distance from each other is a good thing, but tempting bears into our camp zones will teach the bears and their young that there is easy food to be had and will create a habit for them.
Are problem bears the result of bears being bad or people “teaching” them bad habits? Think about it. If we leave our food out for them to smell they will naturally be curious and come within a closer proximacy than anyone would like. If we teach the bears that camp food is easy and tasty they will keep coming back creating problems for future campers and hikers.
So at the end of the day, no matter how tired you are please hang your food. Many park areas do supply easy hanging pulleys and all you have to do is gather your food into a cache with a hook (or bag with a good drawstring) and clip it onto the pulley system to hang.
Alternately, we've also backpacked where no hanging pulley was available but a ground height food cache locker was.
Before you head out into the back country check to see if the area has a food cache system in place that you can use. If not, you must provide your own and make sure to protect your food from tempting the bears.
Teaching bears to come closer to hikers and campers for human food is dangerous for humans and teachers the bears very bad habits while endangering them at the same time.
Please do not feed the bears.