A key to strengthening spiritual muscles and enduring hardship is finding strength in the Word of God.
However, the Bible is called the Word of God because the whole transcript is an inspired, faithful, and infallible record of what God determined essential for us to know about Himself, the cosmos in which we live, our spiritual allies and adversaries, and our fellow man.
What makes you a Christian is whether or not you really are in accord with biblical theology and whether you know Jesus Christ as your Saviour.
The Doctrine of the Trinity teaches that within the unity of the one Godhead there are three separate persons who are coequal in power, nature, and eternity.
The moment you enlist in the army of God, you personally become a target. You need to remember that if you're living for and walking with Jesus Christ, the powers of darkness are aligned against you.