First off it's important in this passage to realize that both the belief and the suffering is a gift from God. When Paul says it has been granted, he is showing that by God's grace he has enabled you to believe and to suffer. Does this mean we just trust the Lord and not worry about preparing to suffer? Allow me to suggest a few things to consider.
1. We will only suffer well when we trust in a sovereign God. What I mean is that if we don't believe that God is in control of all things then we will have a hard time trusting Him when it appears He's nowhere to be found.
2. We must walk close enough to God and trust in His promises so that when suffering come and we don't feel Him we can know He's still there. For instance, God will remain faithful for He cannot deny Himself. God will never leave those who are His. God will work all things for good for those who are His. God is in control and can do whatever He pleases.
3. Trust that faith is more than a feeling. There will be times in our lives where we do not "feel" God's presence. However, He's there! Exercise your faith and trust that God is accomplishing something for you joy and His glory.
4. If suffering is a gift, then we should expect it and not be caught off guard from it.
5. Remember that as Christians, we want to suffer for the sake of Christ. We will never do this if we don't know Him.
That is not exhaustive. I'm sure there are many other things to say. What else would you add or take away as we prepare for suffering for the glory of Jesus Christ?