When we hunger and thirst for things in this world (sex, materialism, power, honor, etc.), it's an indicator that we long for something even greater and better than all of those things- God. Real nourishment (which is actually a spiritual type of nourishment) comes from doing the will of God.
I hope this song will encourage you- "Give us clean hands" by Chris Tomlin:
Worship God only and give Him thanks. Don't commit idolatry by lusting after an object's/person's beauty. This will prevent your mind from becoming dark, confused (refer Romans 1:21-24), and enslaved to sin. Jesus also emphasized much on inner purity today which even many Christians (i.e. carnal Christians) ignore today. Our psychological and spiritual power to succeed against sin and the ability to succeed in our education/careers starts with taming our thoughts (refer to Mark 7:20-23). Many times, I've wished that I could be like the Jedi who were empowered by the Force in the fictional universe of Star Wars. God helped me realize that He is the real Force (power) that exists today and He wants to empower us. Thus, take heart (be encouraged) by the truth that the Holy Spirit can empower you to overcome everything you face in life (ex. sins, problems which seem impossible to overcome) if you will allow Him to come and live in you (refer to John 14:15-17).
Demonic spirits are responsible for attacking you with fear, anxiety, depression, covetousness, lust, envy, hatred, etc. Whenever you face such negative thoughts, learn to recognize that it is Satan and his demons working through the world around you to attack you with their spiritual flaming arrows designed to destroy you mentally/spiritually. In order to defend against their spiritual/psychological weapons, you must take up the armor of God (refer to Ephesians 6:10-18). You need the "shield of faith" to defend against the fiery darts of fear, depression, lust, envy, etc. As your offensive weapon, you also need the "Sword of the Spirit" which is the word of God (Scripture aka the Holy Bible) to fight back against Satan, his demons, and the evil people in this world they use to attack your mind (it's psychological warfare). When you are tormented by any negative thought, the Body of Christ is being attacked also. Remind evil spirits of that truth. That should instill fear in them as they are messing with Christ's body. Hence, when they try to instill fear in you, you can instill fear back in them as they all fear God. Their main strategy is trying to throw you off balance continuously by taking your mind off of God. Our tendency is for us to sink in fear even when we think we are standing strong in God. If you sink in fear, it means you're not standing strong in God as you lack faith. You fight fear and depression with faith. Thus, if you want to remain unshakable, you must have an unshakable faith even when Satan, his demons, and the world around you tries to instill fear in you (think of it as them throwing objects of fear at you but you standing fast by faith and knocking down everything they throw at you).
Mark 7:20-23 (NLT):
"And then he added, “It is what comes from inside that defiles you. 21 For from within, out of a person’s heart, come evil thoughts, sexual immorality, theft, murder, 22 adultery, greed, wickedness, deceit, lustful desires, envy, slander, pride, and foolishness. 23 All these vile things come from within; they are what defile you.”
Refer to my other post also regarding lust ("A perspective to overcome lust") for a more detailed discussion.
Bible passage for reference:
John 4:10,13-15,31-38 (NLT):
"Jesus replied, “If you only knew the gift God has for you and who you are speaking to, you would ask me, and I would give you living water.”
13 Jesus replied, “Anyone who drinks this water will soon become thirsty again. 14 But those who drink the water I give will never be thirsty again. It becomes a fresh, bubbling spring within them, giving them eternal life.”
15 “Please, sir,” the woman said, “give me this water! Then I’ll never be thirsty again, and I won’t have to come here to get water.”
31 Meanwhile, the disciples were urging Jesus, “Rabbi, eat something.”
32 But Jesus replied, “I have a kind of food you know nothing about.”
33 “Did someone bring him food while we were gone?” the disciples asked each other.
34 Then Jesus explained: “My nourishment comes from doing the will of God, who sent me, and from finishing his work. 35 You know the saying, ‘Four months between planting and harvest.’ But I say, wake up and look around. The fields are already ripe for harvest. 36 The harvesters are paid good wages, and the fruit they harvest is people brought to eternal life. What joy awaits both the planter and the harvester alike! 37 You know the saying, ‘One plants and another harvests.’ And it’s true. 38 I sent you to harvest where you didn’t plant; others had already done the work, and now you will get to gather the harvest.”