Your compliments to employees should motivate them. Sometimes, however, it can have a negative effect.
Here's how your praise really works:
Don't praise without sincerity. Don't always say that people are great before you criticize them. This will make people feel that the praise you said before is not sincere. You need to focus on building a truly sensible relationship with your employees, and what you say to them should be felt from the heart.
Praise his efforts, not his personal qualities. If you always praise a person's wisdom and talent, it's easy to keep him in comfortable areas. In contrast, if you can point out what efforts he has made and what problems he has solved, why can you agree with him to do so, clearly point out, you can win his respect, and have the motivation to continue to enhance his progress.