7. Hang out with other people who belittle you.
Friendly banter is one thing, but there are people who seem to thrive on tearing others down. The more time you spend with them the more they will affect your state of mind. Philippians 4:8 instructs - "Finally, brethren, whatever things are true, whatever things are noble, whatever things are just, whatever things are pure, whatever things are lovely, whatever things are of good report, if there is any virtue and if there is anything praiseworthy--meditate on these things."
8. Keep doing the same thing over and over again; never learn anything new.
It is possible to get in a rut and lose focus. Ecclesiastes 1:9 reads - "That which has been is what will be, that which is done is what will be done, and there is nothing new under the sun." Schedules and habits are good, but so is changing things up once in a while. Learning new things can help keep life fresh as well as being reminded of life's purpose (cf. Eccl. 12:13,14).
9. Be lazy and follow the path of least resistance.
God created us to work and be active. Being lazy does not lead to good mental health. The book of Proverbs has much to say against being lazy, for example, 13:4 - "The soul of a lazy man desires, and has nothing; but the soul of the diligent shall be made rich."
10. Hold on to anger; never forgive anyone.
Some hold on to anger for weeks, months, and even years. God says such is not good! Ephesians 4:26 - "Be angry, and do not sin: do not let the sun go down on your wrath." In other words, take care of the problem today.
11. Always be right; never let anyone else be more right than you.
Those who are full of pride and unwilling to admit mistakes will not have real joy. Proverbs 13:10 - "By pride comes nothing but strife, but with the well-advised is wisdom."
12. Compare yourself unfavorably to those who you feel are more successful or more blessed than you.
This is not productive. In the parable of the talents in Matthew 25, you don't find the servant who received two talents complaining about the five talents a different servant received. Instead, what did he do? He went out and used his talents faithfully. There's an important lesson there, friends.
13. Let small issues snowball into big problems.
Just ignore the small problems and hope they will just go away on their own--that's foolish! If you have been offended or if you believe you have offended someone else, you have a duty to go to them and try to correct the problem while it is still small (cf. Matt. 5:23,24). There is great wisdom in solving problems sooner rather than later, and this is true physically and spiritually.
14. Never take responsibility for your own actions; instead blame everyone around you.
This will not lead to a positive state of mind (e.g., Gen. 3:11-13).
15. Don't let anyone help you.
Being so proud that you won't accept help that anyone offers and you won't ask for help when you really need it is foolish. Galatians 6:2 - "Bear one another's burdens, and so fulfill the law of Christ."
16. Quit when the going gets tough.
If you give up when things get challenging you'll waste so much of your potential. Jesus taught in Matthew 10:22 - "He who endures to the end will be saved."
17. Get four or five hours of sleep every night and convince yourself that it's enough.
You might be able to get by for a couple nights, but the human body needs more rest than that for overall health. Studies have shown this repeatedly. 7 - 9 hours is recommended for most adults. More than that is not necessarily better though. It's possible to go to the other extreme as Proverbs 6:9 addresses - "How long will you slumber, O sluggard? When will you rise from your sleep?"