“…For this purpose the Son of God was manifested, that he might destroy the works of the devil.”  
1John 3:8

Jesus had made clear what the works of God were while he walked on the earth:
“…but that the works of God should be made manifest in him. I must work the works of him that sent me, while it is day: the night cometh, when no man can work.” John 9:3-4
After he made that statement, he went ahead and healed a blind man, so the fact that the man was blind wasn’t the work of God, it was the work of Satan, his job description rightly defined by Jesus:
“The thief cometh not, but for to steal, and to kill, and to destroy:…” John 10:10
“How God anointed Jesus of Nazareth with the Holy Ghost and with power: who went about doing good, and healing all that were oppressed of the devil; for God was with him.”  Acts 10:38
In the main verse, he makes clear that Jesus came to destroy, render ineffective, the works of the devil and his method of doing that was to make the divine life available, such that if any man would receive that life, all of the works of Satan would be permanently ineffective in his life.
“…I am come that they might have life, and that they might have it more abundantly.” John 10:10
“…whosoever believeth in him should not perish, but have everlasting life.” John 3:16
If you have received that life, then rest easy, nothing the devil throws can be successful against you, once it comes in contact with you, it has only one end- “ineffective and destroyed”