"Let go and let God" can be taken to mean a couple things, so we will deal with each meaning separately.
Should a Christian 'Let go and let God'?
One popular meaning of letting go is to passively sit back and simply allow things to happen. This is typified by the fatalistic "Que sera sera" (Whatever will be, will be). This attitude says, "There's nothing I can do, so why try?" Even though it is absolutely true that God is sovereign and in control of everything, this approach is definitely not biblical. We are commanded in Philippians 2:12 to "work out [our] own salvation with fear and trembling." Paul commanded Timothy to "Fight the good fight of the faith. Take hold of the eternal life to which you were called and about which you made the good confession in the presence of many witnesses" (1 Timothy 6:12). We are told, in Ephesians 6:10–18 where the armor of God is detailed, to put on the armor of God and stand against the schemes of the devil. These are just three commands in the Scripture that say that we have a responsibility to do something, not just sit back and watch things happen. So the passive interpretation of "Let go and let God" is certainly not right to do.
A second interpretation is that we should stop trying to control our circumstances and trust in God to control them. This is biblical.
When it comes to our needs, Jesus said in The Sermon on the Mount, "Therefore do not be anxious, saying, 'What shall we eat?' or 'What shall we drink?' or 'What shall we wear?' For the Gentiles seek after all these things, and your heavenly Father knows that you need them all" (Matthew 6:31–32). Instead, we should "seek first the kingdom of God and his righteousness, and all these things will be added to you" (Matthew 6:33). So we should not obsess over our needs—God will take care of them. On the other hand, we do have the responsibility to work toward meeting our needs. As Paul wrote to the Thessalonians, "we would give you this command: If anyone is not willing to work, let him not eat" (2 Thessalonians 3:10). God will meet our needs. If He gives us the ability to work and "provide" for ourselves and our loved ones, that may be the way He has chosen to meet our needs, and we have an obligation to Him to exercise the abilities He has given us. But we should realize that He is meeting our needs, not ourselves.
We also have the responsibility to do the work that He has provided for us. Ephesians 2:10 says, "For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them." We are expected by God to do the good works He has prepared beforehand for us. He will provide what we need to do that. These "good works" include building up the body of Christ. Paul wrote in Ephesians 4:11–12 that Jesus "gave the apostles, the prophets, the evangelists, the shepherds and teachers, to equip the saints for the work of ministry, for building up the body of Christ." First Corinthians 12:7 says, "To each is given the manifestation of the Spirit for the common good." So God gives people and gifts (manifestations of the Spirit) to the church.
So, if "Let go and let God" means that we don't try to control our situation or meet our needs in our own strength but surrender to God in His sovereignty, it is definitely biblical. It is also very hard to do. As a matter of fact, it is impossible to do without God's enabling us to do it. In God's power, we can surrender to Him and thus "Let go and let God."
How can we turn worries and problems over to God?
Is it true that God will not give us more than we can handle?
Why should I trust in God and how can I learn to trust in Him?
How is God sovereign and humans have free will? How do free will and God's sovereignty work together?
What is the key to knowing the will of God?
Truth about the Christian Life