I struggled for a long time with the Spirit-filled words of Romans 9:14-24:
'What shall we say then? Is there unrighteousness with God? Certainly not! For He says to Moses, “I will have mercy on whomever I will have mercy, and I will have compassion on whomever I will have compassion.” So then it is not of him who wills, nor of him who runs, but of God who shows mercy. For the Scripture says to the Pharaoh, “For this very purpose I have raised you up, that I may show My power in you, and that My name may be declared in all the earth.”
Therefore He has mercy on whom He wills, and whom He wills He hardens. You will say to me then, “Why does He still find fault? For who has resisted His will?” But indeed, O man, who are you to reply against God? Will the thing formed say to him who formed it, “Why have you made me like this?” Does not the potter have power over the clay, from the same lump to make one vessel for honor and another for dishonor? What if God, wanting to show His wrath and to make His power known, endured with much longsuffering the vessels of wrath prepared for destruction, and that He might make known the riches of His glory on the vessels of mercy, which He had prepared beforehand for glory, even us whom He called, not of the Jews only, but also of the Gentiles?'
After lots of wrestling and struggling with God I had to accept these words. I can't ignore it or call it obscure and without relevant meaning. If you believe this paragraph of the Bible you will start to expereince God as bigger and more precious than you ever imagined.
One of the best books on the Sovereignty of God by A W Pink: Buy, read online.
Scriptures proving the Sovereignty of God here.
A simple definition of the Sovereignty of God here.
Piper resources on the Sovereignty of God here.