Satan is the reason that there is sin in this world. Without him, the world would have been without sin or evil of any kind. But, while Satan is the reason behind the bad things that happen, each person is responsible for his or her own actions. Consider Adam and Eve. If Satan had not tempted them, they would have never conceived of disobeying God. But they could have chosen to honor the Lord by not sinning.
God wants man to freely choose Him. What good is obedience if it is only obtained through force? God wants us to choose with our whole hearts to worship Him. Because of that desire, He gave us free will. Obeying God is an act of worship when it is done without force. God will not force us to worship Him nor will He allow Satan to force us to sin.
In Luke 4, you can read about how Jesus himself was tempted by Satan. He stood strong in the face of temptation, used the Word of God to support His resolve, and then went on to begin His ministry to all of mankind. Sometimes, God allows us to be tempted in order to strengthen our faith or to confirm our stand for Him. It is important to determine in advance how you will react in a given tempting situation. Then, study the Word of God on the issue; hide the Word in your heart so that you, like Jesus, can recall it in your time of need.
“Thy word have I hid in my heart, that I might not sin against Thee”(Psalm 119:11).