Being a Christian does not exempt us from the challenges of life. Isaiah 43:2 does not say "If you go through deep waters, I will be with you....", but it says, "When you go through deep waters, I will be with you....". This suggests that there may be those times when you may encounter difficulties that seem overwhelming, or you may have to make difficult decisions and are unsure of how best to proceed. At other times, you may just need someone to pray with you or help guide you in how to move forward according to God's principles.
That is why we are here. To strengthen the weak hands, and make firm the feeble knees. To say to those who have an anxious heart, be strong and do not be afraid. (Isaiah 35:3-4)