The fig tree is a picture of self-effort and self righteousness. In Mark 11, Jesus cursed the fig tree. Self-effort and self righteousness are cursed by God from the day Adam decided to take matters into his own hands. I have recently repented and renounced all covenants and agreements with self effort. But the fig tree didn't instantly wither.
The next thing Jesus did was go to the temple and declare that God's house shall be a house of prayer (Mark 11: 17). Later, when they passed the fig tree, it was dried up from its roots (Mark 11:21).
The lesson I've learned from what Joel is saying here and what my brother Joseph Prince has taught, is after we curse and renounce self-effort, we need to become a house of prayer in our person life, thereby allowing God to clean out our "temple" (body/life). Self effort will wither from its roots. The next thing Jesus talked about was moving mountains by faith (Mark 11:23). Our lives become fruitful, powerful and effective in our dependence on and faith in Him, essentially free of the exercise in grief and futility of self effort and self righteousness.
God Bless.