PSALM 138
3. In the day when I called, You answered me, and strengthened me with strength (might and inflexibility) to temptation in my inner self. Amp.
8. The Lord will perfect that which concerns me: Your mercy and loving kindness, O Lord, endure forever; forsake not the works of Your own hands. Amp
This is a Psalm of David. He is not asking for help. He is praising God for His mercies that have been sent. He sees that the Lord has mercy on the lowly. He recalls how the Lord heard his cry and answered him. He is so thankful for the strength he has received from the Lord.
Now he knows that the Lord will always answer and will perfect all that is wrong in David. He is so thankful for all the Lord has done. He has learned how good the Lord is and knows no matter how much trouble he walks in the Lord will fight his enemies and provide a safe landing for him.
That is the reason for our trials. We need to see the Lord work for us personally. Then we will believe Him, trust in and rely upon Him just like we need to do. That is why He wants us to be thankful and rejoice in our trials. They really are blessings.