John 16:33 (and multiple others)
We are one of 2 things as a Christian - a conformer (shaped from without) or a transformer (changed by power within).
If we recognize that the biggest obstacle we have to overcome is ourselves we are way ahead of the game. What overwhelms and discourages me are those things that keep us from being what He wants us to be.
We have the power to overcome if we do not fall prey to those obstacles of self but immerse ourselves in His grace and love.