Remember the Lord your God. He is the one who gives you power to be successful, in order to fulfill the covenant he confirmed to your ancestors with an oath (Deuteronomy 8:18).
Why does God allow suffering in our lives? Why does He allow us to experience adversity?
One purpose, I believe, is to keep us humble. Prosperity and success can sometimes make us proud and self-sufficient. We think we don't need God, because we have our salary... we have our investments... we have our health... we have our family... we have a successful ministry.
But when the economy goes south or the stock market crashes or our home burns down, we turn to God, and we are reminded of what really matters.
Before the Israelites entered the Promised Land, God warned them,
"Beware that in your plenty you do not forget the Lord your God and disobey his commands, regulations, and decrees that I am giving you today. For when you have become full and prosperous and have built fine homes to live in, and when your flocks and herds have become very large and your silver and gold have multiplied along with everything else, be careful! Do not become proud at that time and forget the Lord your God..." (Deuteronomy 8:11-14)
I think we should pray for success in what we do, but I also think it is right to say, "Lord, Your will be done." Sometimes God will not allow us to be successful in our efforts.
It is better to fail and turn to God than to succeed and forget Him. That doesn't mean we always have to fail. But the doorway to success is often through the hallway of failure. And failure has its place, because it is part of a learning process.
Sometimes God may allow us to fail or experience hardship so we will trust in Him.