The Bible gives us a clear picture of evil: because of our wicked, evil ways, God sent His Son to save us from our sins (Titus 2:11-14); Paul tells us that we live in “this present evil age (Galatians 1:4); as followers of Christ, we’re in a constant battle against evil.

For we are not fighting against flesh-and-blood enemies, but against evil rulers and authorities of the unseen world, against mighty powers in this dark world, and against evil spirits in the heavenly places.
Ephesians 6:12, NLT

God calls us to overcome evil, so we know it is possible. He even tells us what weapon to use:

Do not be overcome by evil, but overcome evil with good. Romans 12:21, NIV

Observe that the text [above] appears to give us a choice between two things, and bids us choose the better one. You must either be overcome by evil, or you must yourself overcome evil: one of the two. You cannot let evil alone, and evil will not let you alone. You must fight, and in the battle you must either conquer or be conquered. The words before us remind me of the saying of the Scotch officer to the Highland regiment when he brought them up in front of the enemy and said, “Lads, there they are: if ye dinna kill them they’ll kill you.” So does Paul marshal us in front of evil, and like a wise general he puts us on our mettle by saying, “Overcome, or be overcome.” There is no avoiding the conflict, no making truce or holding parley, no suspension of hostilities after a brief skirmish, but the battle must be fought through to the end, and can only close with a decided victory to one or the other side. 

~ Charles Haddon Spurgeon, Sermon No. 1317, Metropolitan Tabernacle Pulpit, Volume 22

As Christians, we need to learn to depend solely on God to engage in a daily battle to overcome evil, to stay firmly connect to our power source.