When a person commits himself to following the Lord, it does not mean that every thing will be easy for him in the future. Even good people who have a deep trust in the Lord can find themselves losing confidence when circumstances are tough, becoming anxious about the future or the past, or struggling with negative attitudes or evil thoughts.
The Bible has a great deal to say about the spiritual trials that we have to face, and we can find there the way to come through those struggles a stronger and better person.
We have these trials or temptations because spiritual growth is gradual. Just as it takes many years to become physically mature, it also takes many years to become spiritually mature. Love for the Lord and love for one's neighbor are not static qualities; they grow stronger and more perfect over the course of one's lifetime. In the mean time, our old, evil thoughts and self-centered habits still have an influence upon us. The result is a conflict between the "old man" and the "new man" (Ephesians 4:22-24), a struggle between the "flesh" and the "spirit." "The flesh lusts against the spirit and the spirit against the flesh; and these are contrary to one another, so that you do not do the things you wish." (Galatians 5:17)
The reason the flesh or the worldly mind acts against the spirit or the spiritual mind is that evil spirits in hell influence us by means of our worldly and physical desires. So Paul spoke of the "thorn in his flesh," which was sent by Satan to buffet him. (2 Corinthians 12:7) Temptations are actually caused by the struggle of devils against angels to gain influence over us. "For we do not wrestle against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this age, against spiritual hosts of wickedness in the heavenly places." (Ephesians 6:12) So temptation is not just worldly trouble, but inner, spiritual struggle. "For though we walk in the flesh, we do not war according to the flesh. For the weapons of our warfare are not carnal, but mighty in God for pulling down strongholds, casting down arguments,...bringing every thought into captivity to the obedience of Christ." (2 Corinthians 10:3-5) Temptation is a test of our new will, a test which only a regenerating person can undergo. So Peter tells us to suffer not "as a murderer, a thief, an evildoer, or as a busybody in other people's matters," but rather "as a Christian." (1 Peter 4:15, 16) The best example of this kind of temptation is the Lord's own temptations. During Jesus's forty day trial in the wilderness the devil endeavored to gain dominion over Him by appealing to selfish and worldly motives. (Matthew 4:, Luke 4)
As hellish spirits continue to influence us, we may feel more and more anxious, confused, frustrated, or hopeless about our efforts to do what is right. Then we can identify with passages like these: "Have mercy upon me, O Lord, for I am in trouble; My eye wastes away with grief, yes, my soul and my body!. For my life is spent with grief, and my years with sighing. My strength fails because of my iniquity." (Psalm 31:9,10) "My heart is severely pained within me, and the terrors of death have fallen upon me.... And I said, `Oh, that I had wings like a dove! For then I would fly away and be at rest. Indeed, I would wander far off, and remain in the wilderness. I would hasten my escape from the windy storm and tempest.'" (Psalm 55:4-8) At length, we may feel doubtful about whether God is willing or able to help us. "And I said, `My strength and my hope have perished from the Lord.' Remember my affliction and my misery." (Lamentations 3: 18-19) It may seem like the Lord no longer cares for us. "Lord, why do you cast off my soul? Why do you hide Your face from me?" (Psalm 88:14) It may seem that our prayers go completely unanswered. "My God, my God, why have You forsaken me? Why are You so far from helping me, and from the words of my groaning? O my God, I cry in the daytime, but You do not hear; and in the night season, and am not silent." (Psalm 22:1-2)
The Bible tells us not only the nature of temptation, but how to overcome in temptation. Basically, there are two things we need to do. One is to turn to the Lord for help. The other is to actively resist the evil within ourselves.
Turn to the Lord and ask Him for help, recognizing that only the Lord can save you. "As for me, I will call upon God and the Lord shall save me. Evening and morning and at noon I will pray, and cry aloud, and He shall hear my voice. He has redeemed my soul in peace from the battle which was against me, for there were many against me." (Psalm 55:8) Only the Lord has power to overcome hell. We need to recognize that we are completely powerless on our own, and that the victory belongs to Him. "Power belongs to God." (Psalm 61:11) It is through Him that we conquer. (Romans 8:37; 1 John 5:4) The Lord your God is He who goes with you, to fight for you against your enemies, to save you." (Deuteronomy 20:4) "The Lord will fight for you, and you shall hold your peace." (Exodus 14:14) We can pray as David did, "Give us help from trouble, for vain is the help of man. Through God we will do valiantly." (Psalm 60:11) So "cast your burden upon the Lord, and He shall sustain you." (Psalm 55:22)
All our strength in temptation is from God. It is the Lord's power, but He lets us use it as if it were our own. So to let the Lord work in us, we have to actively fight our evil inclinations and impulses. The first step in resisting evil is to identify it by self-examination. "Let us search and try our ways, and turn again to the Lord." (Lamentations 3:40) "Examine yourselves, whether you are in the faith." (2 Corinthians 13:6) "Consider your ways." (Haggai 1:7)
The next step is to be on guard against the evil impulses you have identified. "Watch and pray, lest you enter into temptation. The spirit indeed is willing, but the flesh is weak." (Matthew 26:41) "Be vigilant!" (1 Peter 5:8) "Take heed to yourselves, lest you heart be deceived." (Deuteronomy 11:16)
And finally, when you feel an urge to think or do what you know you should not, resist. Fight it! Don't give in. "Resist the devil and he will flee from you." (James 4:7) "Resist him, steadfast in the faith, knowing that the same sufferings are experienced by your brotherhood in the world." (1 Peter 5:9) By using the power of God we can "fight the good fight." (1 Timothy 1:18) "Put on the whole armor of God, that you may be able to stand against the wiles of the devil.... Stand therefore, having girded your waist with truth, having put on the breastplate of righteousness,... taking the shield of faith,...and the sword of the spirit, which is the Word of God..." (Ephesians 6:11-17) Spiritual temptation at times involves desperate inner struggles. Yet you can know that the Lord is always with you, "a very present help in trouble." (Psalm 46:1) You can know that "after you have suffered a while," the Lord will "perfect, establish, strengthen, and settle you." (1 Peter 5:10) "Commit your way to the Lord, trust also in Him, and He shall bring it to pass." (Psalm 37:5)