Things we can't ever seem to get right

I do admit some of these might be a result of my ineptitude at basic life skills, do let me know if you agree with any one!

1. How many times to call a person back after they hung up on you in anger
2. The perfect cozy-under-the-duvet AC temperature
3. That one drink to stop at to avoid the hangover the next day
4. How to deal with those who annoy us, without letting them affect us
5. The choice of person to lose your virginity to - a choice that would seem correct at age 30
6. The optimal number of shoes to pack on a vacation
7. Accurate microwave settings and timings
8. How short to cut your hair before it becomes too short
9. Whether to reply to a text message signaling the end of a conversation, or not reply and be labeled a snob.
10. The exact volume to set on the TV without having to readjust it every few minutes
11. How many cheese puffs to have before you feel sick
12. How more-or-less frequently must you text the person you're thinking of all the time
13. Knowing exactly how many onions will constitute one kilo - to avoid the vegetable seller seeing right through your n00b-ness
14. How much tip to leave after a meal - without hurting server sentiments, and your wallet.
15. Whom never to trust too easily, and whom to dare trust with you life.