When it comes to pessimism versus optimism, the Bible doesn’t leave us many options. If we believe in God we can't help but be optimistic — because, regardless of what may happen today, we know that ultimately every thing will work out for our good and God’s glory.
Paul was an optimist. Even as he sat in a Roman jail, he could see the benefits of his imprisonment. He had no promised release date to look forward to, the prison conditions were less than ideal, yet he remained positive about the future.
Read his words in Philippians 1:12-30--Everything that has happened to me has helped spread the Good News. Because of my imprisonment, many of the Christians here have gained confidence and become more bold. I will continue to rejoice. For I know that as you pray for me and as the Spirit of Jesus Christ helps me, this will all turn out for my deliverance. For to me, living is for Christ, and dying is even better.
These aren’t the words of a doomed man. Paul expected the best for tomorrow because he believed in a God who is good, who is powerful, who is merciful, who is love.
Pessimism might come quite naturally to you, but the excuse “It’s just my nature,” doesn't work, any more than we can excuse away lust, laziness, or greed. The bottom line is that pessimism is a sin. It reveals a lack of faith; anything that is not from faith is sin. [Romans 14:23]
Optimism is a choice. I don't believe it comes naturally to anyone. Those who maintain a perpetually positive outlook on life have learned to make that choice.
If Paul can be optimistic in a Roman dungeon, then we shouldn’t let a few minor obstacles ruin our day. We can make the same choice he made: we can choose to expect the best for tomorrow, in spite of what is happening today, because we know that God is good.