Progression of time when velocity is very high

[Epic Sandwich]

So, I understand that the faster you go, the slower time progresses for you. Eg, the hand on your watch would go slower. However, what does this really mean? Would you age slower, meaning biological operations would go slower? Would you, in a way, think slower seeing as the neurones in the brain may transmit thoughts slower? If so, surely you would perceive time going at the same speed as normal?

I'm sorry if this sounds complete rubbish, it was just something I was thinking about.

[Ich]

So, I understand that the faster you go, the slower time progresses for you.
No.
The faster you go as seen by an observer, the slower your time progresses as seen by said observer. That's not just an illusion, however, as the accumulated effect and be measured.

If so, surely you would perceive time going at the same speed as normal?
Yes, that's a tenet of relativity. It only happens to other people. They see their time as normal, you see your time as normal, but you see their time slow, they see your time slow. It's about relations, not malfunctioning clocks.