There is an expression which says, "If you think you're green, you'll grow. If you think you're ripe, you'll rot." Essentially this means that if you think you've reached the point in life where you know it all, you'll disintegrate. This is not a rebuttal of self confidence. However there is a difference between self confidence and arrogance or haughtiness. Perpetual humility is always a noble trait.
There is description of a haughty church in the Bible. In Revelation 3:17, the people of the church at Laodicea were listed as saying, "I am rich, and have become wealthy, and have need of nothing." On the other hand, Jesus sees this congregation in a different light, stating, "...you do not know that you are wretched and miserable and poor and blind and naked" (same verse). Hence they thought they were ripe. Jesus felt they were rotten.
Although I am getting older and am looking forward to retirement one day, it has dawned on me that I will never really retire. There is always going to be more for me to learn in the future, more ministry, and, hopefully, more inspirational writing. I should always remain green.
So, still lots of learning to do, whether it comes from life experiences such as cancer survival or general knowledge obtained from the daily struggles of life. Kermit the Frog sang a song entitled, "It's Not Easy Being Green." Yet, I would much rather be green than rot on the vine.