Jesus died and rose again. The only way to keep going in the Christian life is to keep preaching this gospel to yourself.
The work God has given us is absolutely impossible. But he is the God of the impossible; Jesus died and rose again. He's the God who brings life from death. So the impossible is not only possible, but the very heart of what we are and what we do. Without it Christianity wouldn't be what it is.
Many challenges. Many road-blocks. Many stumblings. Here in Kenya the work of planting credible, Bible-based, loving, fellowshipping, Christ-centred, evangelistic, holy churches seems to have hardly begun. There are "churches" and "Christians" everywhere; but the "Christianity" is little more than lots loud noise, excitement and wide-scale heresy (mostly of the "health and wealth" kind). Protestant Christianity has been here for 140 years - but the culture at large has hardly been touched: corruption, theft, lying, cheating and fornicating are the norm everywhere you turn. It seems hopeless.
But in fact our God is the God of the hopeless. He brings life from the dead. Jesus died and rose again. Glory and resurrection come following death.
I think it's John Calvin who described the work of a minister as being a "living death". When I was a boy, it looked a terrible work to me and I had no desire to go near it. Later, God changed my thinking. It's a glorious work, as well as a terrible one! But the terrible side is all temporary, and the glory is forever. Jesus died and rose again - never to die any more. When the great day of testing and judgment comes, the empty riches of this world will be burnt up as useless stubble. The work of Jesus will remain.