Why is it some believers always seem gloomy and pessimistic?
Often it's because they see their core identity defined by the fact they're sinners.
Yes, we've all sinned and fall short of the glory of God.
But being a sinner isn't what determines your identity.
Our primary identity is molded by the truth God created us as His image-bearers.
And though we're fallen image-bearers, Jesus has redeemed us so we can carry out His purpose in the world -- and do so joyfully.
Now may the God of hope fill you with all joy and peace in believing, so that you will abound in hope by the power of the Holy Spirit (Rom.15:13).