Why is lack of faith such a common struggle?

TL;DR:

Faith is hard because we're constantly battling the world, our own sinful desires, and spiritual opposition. But the more we know God through His Word and walk with Him daily, the stronger our faith grows—and He remains faithful even when we waver.

what does the bible say?

As Christians, we are to “walk by faith, not by sight” (2 Corinthians 5:7), and in Hebrews 11:1, we are told: “Now faith is the assurance of things hoped for, the conviction of things not seen.” Faith is so important that it is impossible to please God without it (Hebrews 11:6). Focusing our minds on God’s proven character and faithfulness to us in the past can strengthen our faith (Psalm 33:4) so we avoid disregarding His faithfulness as the Israelites did (Exodus 32:1-6). We can also increase our faith by growing in our knowledge and understanding of the Word of God (Romans 10:17), which is our spiritual “shield of faith” amid spiritual warfare (Ephesians 6:16). Additionally, even if we have times in our Christian walk in which we are faithless, God still remains faithful (2 Timothy 2:13). Through God’s gift of grace, we have been saved through faith (Ephesians 2:8).

from the old testament

Our faith naturally ebbs and flows, but we must stay close to Christ. Even the Israelites struggled with their faith in the desert after God had freed them from slavery in Egypt and led them safely through the wilderness (Exodus 32:1-6).
We must always keep in mind the goodness of God and how He has been faithful to us in the past: "For the word of the LORD is upright, and all his work is done in faithfulness" (Psalm 33:4).

from the new testament

Romans 10:17 says: "Faith comes from hearing, and hearing through the word of Christ" We can hear the Word by going to church, spending time in personal Bible reading and prayer, listening to sermons online, or being part of a Bible study, to name a few.
While we can easily grasp a truth for which we can see the full physical evidence, the truth of the gospel is one that cannot be seen in the flesh but must be believed (2 Corinthians 5:7).
We are to walk by faith as Christians. In fact, it is by God's grace, through faith, that we are saved (Ephesians 2:8).
The faithful will be opposed by the world, the flesh (sinful desires), and the Devil and his demons. We can resist that opposition by taking up the Word of God, which is the shield of faith: "In all circumstances take up the shield of faith, with which you can extinguish all the flaming darts of the evil one" (Ephesians 6:16). God’s Word helps us to remember His faithfulness, giving us continued confidence in His goodness.
We will always have doubts or struggle with a lack of faith. The good news is that even when we feel faithless, God will always be faithful to us (2 Timothy 2:13).
Faith is not blind belief that is supposed to exist without any proof or evidence. Rather, faith is total confidence—a belief that is grounded in trusting the person of God and His character. This confident trust grows over time. The struggle with faith enters the picture when we try to balance truths we can see with truths that we cannot see (Hebrews 11:1).
Hebrews 11:6 says: "And without faith it is impossible to please him [God], for whoever would draw near to God must believe that he exists and that he rewards those who seek him." Walking by faith requires practice—it does not just happen on its own. Faith is like a muscle that needs to be strengthened.

implications for today

Christianity is entirely founded on a belief in God that is activated by putting our faith in the works and person of His Son, Jesus Christ. The Bible serves as a record of God's faithfulness to people since creation and a signpost of His faithfulness that is yet to come. The primary cause for our lack of faith is that we do not have an actual relationship with the God we claim to put our faith in. Just as we don't trust strangers in our day-to-day interactions, we cannot fully trust a God who is a stranger to us. As we invest in our relationship with God, we get to know Him better and develop a greater level of trust in Him and His ways because we see them in action. It's hard to place faith in someone who is a stranger to us. The answer is to get to know God.

understand

Believers’ faith is often challenged by the world, the flesh (sinful desires), and spiritual opposition.
Regularly studying and meditating on God’s Word strengthens our faith.
A consistent prayer life builds a relationship with God and strengthens our faith.

reflect

What are some challenges you’ve faced with your faith? How did you respond?
How has your personal Bible study impacted your faith?
How has increasing your knowledge of God’s character helped your faith?

engage

What are some cultural influences that might impact believers’ faith?
What is the best way to explain what true, saving faith is to unbelievers who confuse it with blind faith?
What behaviors can Christians exhibit to demonstrate their faith to a lost and dying world?