1. Writer's block is an excuse. An athlete goes for a run outside if he can't get to the gym. A writer writes something, even if he thinks it is just mindless drivel, even on those days when writer's block is telling him he can't.
2. When you work on a piece long enough, the characters start walking around in your head. They come with you to work, to the store, on your dates. This doesn't mean you need medication. It might mean your friends and co-workers think you're far too easily distracted.
3. Your partners, parents and friends might want to hear about your writing, but not as much as you want to talk about it. Network with other writers for that.
4. If you're going to try to publish, you WILL have to deal with rejection. It doesn't mean you suck. There are best-selling authors who could wallpaper a room with their "thanks but no thanks" letters.
5. But you WILL need to develop a thick skin to deal with those rejections - thick like a sun-dried lizard. Learn from them, and move on.
6. Writing seriously and holding down a day job is tough. You'll need to get up early or stay up late. You'll be tired and sometimes cranky. If you want it enough, you'll do it anyway.
7. There are never enough hours in the day, but you have to find them anyway. If all you do is work and sit at the computer writing, your word-well will eventually run dry. Make time for the ones you love, the other things you enjoy, and exercise. The best writers interact with the world enough to collect material. If you don't make time for the rest of it, you'll end up with a big butt, frayed relationships, and nothing left to say. Writing is an endurance run, not a marathon.
8. "Write what you know" is good advice. But so is "learn what you don't know so you can write about it."
9. Research matters. If a character's career is a big part of your story, then you'd better research and understand that profession. If the research isn't fun, that's a sign the topic may not be for you.
10. If at the end of the day, you look at what you've written and say "I enjoyed writing that and I'm glad it now exists," then it was worth it, regardless of how many people ever read it.