If you forget to apply deodorant, use hand sanitizer.
When you forget to apply deodorant, Purell® or similar is a good stand-in replacement that you can rub in your armpits, that will kill the bacteria causing the smell.
More Beauty Tips
Using conditioner for shaving cream.
A large bottle of conditioner is cheaper and will last longer than overpriced shaving cream. Additionally, it doesn't dry your skin out as much as shaving creams do.
Avoid long hot showers to prevent your skin from drying out.
Long hot showers dehydrate your skin. Instead, try to bathe in lukewarm water, and when rinsing your face and hair, use cool water.
Wear sunscreen with zinc oxide as the active ingredient.
The most common types of sunscreens are chemical and physical. Chemical sunscreens absorb the sun while the latter sit on top of your skin to reflect the sun's rays. Zinc oxide is the active ingredient found in physical sunscreens, approved by the FDA, and widely encouraged by dermatologists to be used instead of chemical sunscreens.
After shaving, store your razor with the blade submerged in rubbing alcohol.
This keeps it from rusting and you can get many more good shaves before changing blades.