Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if the be any virtue, and if there be any praise, think on these things. - Philippians 4:8
The Bible says many things about the thoughts of man, in several places in the Bible it mentions the thoughts of man being only evil continually. We also read about the importance of thinking on the right things.
Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him. - 1 John 3:15
This verse may seem a little off topic, but I do not believe it is.
Hatred is a choice, not to be confused with anger, which is an emotion.
The Bible also says,
Be ye angry, and sin not: let not the sun go down upon your wrath: - Ephesian 4:26
I believe that these verses prove the distinction, between the two.
If it says that if you hate someone you are a murderer, and it says to be angry, and sin not, which shows that anger in and of itself is not wrong, then that must mean that anger and hatred are not the same thing.
I believe that hatred is a conscious thought, a choice that we can make. We can choose to hate someone because we are mad at them, or we can choose not to.
Going back to anger, when someone hurts you, you do not really have a choice whether to get angry or not, it happens automatically, it is an emotion. What we choose to do with that anger is our decision.
Another thought we tend to have is Anxiety.
Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God. - Philippians 4:6
When it says be careful for nothing, it is not saying to be careless and go around juggling chainsaws, or something like that, it is saying not to worry.
We are not to worry about anything, but instead we are to pray, and talk with God, with thanksgiving, and tell Him what it is that is troubling us, so that He can take care of it.
And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus. - Philippians 4:7
When we do give our anxiety to God, He promises us peace, not necessarily happiness, but peace is a surety.
Many situations that cause us so much angst, are not controlled by our actions, we have no control over them. God does, however, so we can ask God for help, because He actually can help. When we ask God to help us, it turns out so much better than it would have had we solely worried about it. Worry and fear will also take us away from what we should be doing for God.
Worry is a lose lose situation.
There are of course other wrong thoughts addressed in the Bible, such as,
But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart. - Matthew 5:28
This applies to both men and women looking on women and men, respectively.
And,
For jealousy is the rage of a man: therefore he will not spare in the day of vengeance. He will not regard any ransom; neither will he rest content, though thou givest many gifts. - Proverbs 6:34,35
Again, this applies to men and women both
There are plenty of other verses that talk about our thoughts as well.
This brings us to the question, "What should we think about?".
I will repeat the verse from the beginning because it sums it all up quite nicely.
Finally, brethren, whatsoever things are true, whatsoever things are honest, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things. Philippians 4:8
Please remember that we must all beware of what we are thinking. I know that most of the time we do not fully realize what we are thinking, so we should try to be more aware of our thoughts going forward.
I am willing to try if you are.