I replace negative thoughts with positive and empowering thoughts that support my health.

Replacing a thought is harder than it sounds, because thoughts do not leave when evicted. What works rather better is putting something true beside them.

The scan is worrying and you slept well last night. Both hold. The second does not cancel the first and isn't meant to — it stops the first from being the only thing in the room.

Positive rarely means cheerful. Most of the time it means accurate about more than one thing at once, which is a fairer description of any day you have ever had.