根据括号内的汉语提示，完成句子。
1. He didn't _____ (认识到) that he had lost his way until it was very dark.
2. We can't learn English well _____ (除非) we put our heart into it.
3. If you want to be a good speaker, you have to pay attention to your _____ (发音).
4. We are always _____ (面对) different kinds of challenges.
5. Be more _____ (耐心的), then you will succeed in the end.
6. Lei Feng, one of the greatest _____ (士兵), set us a good example.
