I say what I mean, but do I mean what I say?

[Sitifan]

http://www.ariadne.ac.uk/issue23/metadata/
I say what I mean, but do I mean what I say?
What does the above sentence mean?
1. I say what I mean.
2. I mean what I say.
What's the difference in meaning between the above two sentences?
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Thank you very much for your reply.

[Mister Micawber]

.
1. I say what I mean = I express my thoughts accurately
2. I mean what I say = I strongly support my statement
.
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Native English teacher at Mister Micawber's

[Barb_D]

For example, I say to my children: If you don't stop touching that, I'm going to break off your arms and beat you over the head with them.

I accurately expressed my thoughts. I said what I meant to say.
I have no plan to actually break their arms off. I did NOT mean what I said.