"...give thanks in all circumstances; for this is the will of God in Christ Jesus for you." (I Thessalonians 5:18 ESV)
Yes, it says in all circumstances, but it's not about my circumstance. It's about who God is and who I am becoming in Him. My circumstances (both "good" and "bad") are tools He uses to pull me toward Him.
"And we know that all things work together for good to those who love God, to those who are the called according to His purpose." (Romans 8:28 NKJV)
All things work TOGETHER. I love God, and I am called according to His purpose. God works the "good" and the "bad" circumstances together for what He deems to be good for me. His purpose is always good because He is God and He is good.