Never turn back

This memorable metaphor concludes the self study part of the yoga instructor training:

'Turning back is almost like trying to eat what you have vomited. No sensible person would do that. Sometimes, people are tempted to go back to their old ways. They should just stay a little while and think:
"What will I get that's new that I haven't tasted before? Anything? No, the same rotten stuff that once was bitter to me. How can it be tasty now?"
The mind has simply forgotten the bitterness. Now it looks a little tasty. That's the trick of the mind. So, let us never look back, but march on and on until we reach the goal.'
The Living Gita, Sri Swami Satchidananda