Students usually get a crude sense of tai chi quite quickly but never get very good at it. The reason why is simple... There are 3 considerations:
1. The speed/pace determined by your level of excitement.
2. The actual speed that your nervous system can currently handle.
3. How present you really are.
The discrepancy between the 3 is the issue. Your mind/emotions wants to go fast but your nervous system cannot cope. And maybe you're not fully aware because you're thinking about other things