"Without me ye can do nothing"
John 15v5
The Lord Jesus wasn't over emphasising things when He said this, He is telling the plain truth.
So long as we live in this world, we will never be free of the devil tempting us to sin. The reality is that without the help of Christ, we are weak in resisting the temptations to sin by the devil. Do not flatter yourself that in your own strength you can resist. Peter never thought for one moment he would deny Christ but when tempted by the devil to do so, he did. David never imagined he would yield to the temptation of the devil to lust and murder, but he did.
While in the world as believers in Christ we are to serve Him but we can't convict of sin, or give people a heart to either repent or believe on Christ. No matter the spiritual gifts we have, without the help of Christ we can do nothing.
It's no surprise then that Jesus tells us to watch and pray. To watch means to be on guard realising how subtle the devil is in tempting to sin and how much we need Christ's help to resist. It means to be on guard against thinking that by our study, or persuasive powers or anything we do , we can save a sinner. To pray is the most important duty of all. We cannot do anything without Christ's help and the way to get it is by praying for His grace and power. So as believers we need a reality check and realise spiritually, we can do absolutely nothing without the help of Christ.