Having a day pack is essential. Many people never think to pack a small backpack in their suitcase, but once you arrive at your destination they prove invaluable! Carrying water, guides, and camera batteries can be cumbersome and irritating. Hauling around a gift you bought at a market while trying to navigate tuk tuks is tricky at best. Being able to toss these small items in your day pack makes your day much more pleasant.
Travel Gadget Pro Tip: Everything you bring should have more than one purpose. A day pack can serve as an organizer in the suitcase and a day pack on arrival. A small day pack is FAR more secure than a purse, and, can be used as a spare bag if your main bag is ruined or lost.