We will be steadfast and faithful. Our leaf will not wither. This doesn't mean we won't grow feeble with age, but it does mean we will still have the zeal of youth. We will maintain our Christian walk with the same enthusiasm with which we began. This causes us to be confident in all our endeavors.
Confidence breeds success.
Also, we have a helper, the Holy Spirit, who, when we fail, will lead us back toward the road to victory. This verse tells us we are like a tree planted by streams of water. In the middle of the garden was a cistern or well. This water was divided into rivulets to run along the rows of trees so that when it wasn't raining, it could provide a constant supply of irrigation. The wicked are not so, but are like chaff which the wind drives away.