A lot of times in the Christian life, the problem isn't the devil or a friend trying to influence us to do wrong. More often than we would like to admit, the problem is US.
The moment we trusted Christ, it was like nothing else mattered, but serving God! Then a couple of hours passed and something else did matter.
Welcome to the nature of our flesh.
When Christ saved us, he saved our SOUL, not our flesh. This is why the Bible says: "in my flesh, dwelleth no good thing."
Your soul may be done with sin, but that's NOT what your "flesh" thinks. Our "flesh" is not going to change, until we receive our glorified body.
Our struggle, as Christians, is to keep our "flesh" in a dead sate.
Repeat after me: "I die daily!"