Matthew Henry's commentary tells us that is proper to end all prayers with praise! He suggests that we be encouraged by what Jesus has already done for us (the sacrifice for salvation, the conversion of sinners, and the comfort of believers) and continue to ask for more!
In these verses, Paul challenges us to "live close to Christ". In doing so, we affirm our beliefs, renounce the enemy and continue to lift up our praises to the Creator! When we have Jesus at the center of our lives, we place all our priorities under his hand. Our conduct becomes consistent with what we are asked to do: to honor, worship and serve our King!
Christ's church will last through all generations! We are a part of that church and therefore are a part of that "world without end". The doxology in verse 21 is familiar to many, but often it is just a sentence spoken at the end of a request. Focus on the revelation contained in that sentence and be in awe of the miracle it contains!
