1 Thessalonians 5:18
Give Thanks Always
In everything give thanks, for this is the will of God in Christ Jesus toward you.
The verse does not say be thankful for everything. It says give thanks in everything.
That is a different thing altogether.
Some days are lovely and easy to be thankful for. Some days are hard. Somebody was unkind, or you felt unwell, or the thing you had been looking forward to did not happen.
Even on those days there is nearly always something. A warm bed. Somebody who came to find you. Toast.
Looking for the something is a habit, and habits get easier every time you practise them.
Something to talk about: Go round the room and each say three things from today you are thankful for. Small ones count.