Before you have placed your trust in Christ as your Lord and Savior, there is nothing whatever you can do to please God or to gain acceptance with Him. John 3:35 declares that “the Father loves the Son” and cares what you think about Him and do with Him. This is why Verse 36 goes on to say:
“He that believeth on the Son hath everlasting life; and he that believeth not the Son shall not see life, but the wrath of God abideth on him.”
But once you have received Christ as your Savior and Lord there is much you can do to please God. You can witness to His saving grace, you can please Him by living a godly life, you can work for Him, you can sacrifice of your means to further His cause, and yes, you can fight for Him. “Fight for Him” you say? Yes indeed, for this world system, our Adamic natures and Satan and his hosts, are all antagonistic toward the Christ who died for our sins. Satan’s forces, especially, work behind the scenes to “blind the minds of them that believe not” (II Cor. 4:4). These fallen angels, we read, are “the rulers of the darkness of this world” (Eph. 6:12).
This is why God urges His children to be “strong in the Lord,” putting on “the whole armor of God,” so as to meet and defeat these evil forces (Eph. 6:10,11). This is why He puts a sword (“the Word of God”) into our hands and bids us “stand… stand… stand!” (Eph. 6:11-14).
Ah, but a great veteran, who waged many battles in making Christ known to the lost, gives us an inkling of the thrill that goes with being “a good soldier of Jesus Christ.” In his last words, just before his execution, the Apostle Paul declared triumphantly: “I have fought a good fight!” (II Tim. 4:7). It was indeed “a good fight” in which he had been engaged, a fight to bring light and salvation and blessing to benighted souls. And the reward:
“Henceforth there is laid up for me a crown” (II Tim. 4:8). source