How could a person be so 'bastardly' and immatured in his writing when his behaviour was somewhat normal?

and...

How can a person's way of writing changed when his behaviour is still similar to the past?

I refer to behaviour as 'outer' behaviour, what people can see.

However, as thinking is linked closely with writing and behaviour, i think the only mindset changes, not affecting behaviour at all. Sounds totally cheem but it all quite made sense to me. Acting and behaving, thinking and writing, it was all very jumbled up. A muddle. And erm... i guess i got it sorted out a bit.