"Give thanks in all circumstances; for this is the will of God in Christ Jesus for you."
Notice the preposition: in all circumstances, not for all circumstances. Paul isn't asking you to thank God for a diagnosis or a loss as though it were good in itself. He's asking you to keep giving thanks while inside the circumstance, trusting God's presence and goodness even when the situation itself is not good. This distinction frees you from the guilt of not feeling grateful for the hard thing, while still inviting genuine thanksgiving for what remains true regardless — His nearness, His promises, the people around you.
Lord, I give You thanks today, not for every circumstance but in the middle of them. You remain good regardless. Amen.