Judge your problems by Olympics - in 4 years all the stuff you're worried about now will be gone (and probably replaced by new problems)
If you want to learn a new language it's better to practice 15 minutes every day than an hour three times a week.
If you have to spend money on one article of clothing, go with good shoes.
Smile at strangers but keep your shoulders square.
If I didn't understand an interview question (or need some more time to think of a good response), ask "In what context do you mean that?"