You have to be fully convinced. No half-stepping, no “we’ll see how it goes”. It just makes finishing easier. But remember, your conviction may or may not involve your feelings.
As I read Luke’s account of Jesus’ Passion Week it stood out to me that our Lord had to have a strong mind, AND He was fully convinced! Even when He was in anguish and requested another way, He backed up His commitment to God’s way above Himself.
Imagine setting out to do something of great benefit to others (be it a ministry, business, marriage, family, health/fitness goals, a career; or in Jesus’ case – saving humanity from sin and it’s consequence). Imagine having to achieve this only through the worst of obstacles – especially from the potential benefactors of your goal! Meaning that those obstacles are so close to home they’re enough rattle a mind loose.
When you are fully convinced, knowing where you got your mandate from and the end result, you might cry, you might sweat and call out for help. But although quitting may cross your mind you won’t permit it to stay in your mind. You will finish.
“Therefore, since we are surrounded by such a great cloud of witnesses, let us throw off everything that hinders and the sin that so easily entangles. And let us run with perseverance the race marked out for us, fixing our eyes on Jesus, the pioneer and perfecter (some translations use “finisher”) of faith. For the joy set before him he endured the cross, scorning its shame, and sat down at the right hand of the throne of God. Consider him who endured such opposition from sinners, so that you will not grow weary and lose heart.
Hebrews 12:1-3 NIV (empasis, mine)