Big Sister for Hire

As a big sister, I am naturally overbearing, feeling it necessary to tell people how they could be doing things better. This is advice I would like to have given a young man sitting near me at lunch today:

1. When you're sitting outside at a restaurant, you're still at a restaurant, so don't put your feet up on a chair, and don't talk on your phone the whole time.
2. If you have to tell someone that you are mature, like you said to the person with whom you were engaged in a long phone conversation, that probably means you aren't actually mature.
3. If you feel it necessary to justify how much you drink, then the person on the other end of the phone is probably right to tell you that you drink too much.
4. While being friendly is nice, don't try to start a conversation with everyone within 10 feet of you. It just seems a little desperate.
5. Go back to that restaurant and pick up your phone, because you left it on the table.