"Flattery gets you nowhere, but certainly opens many doors."
Voicing the admiration for things other people do is an art itself. It's a balancing act of what was done and how valuable it turned out to be.
Overused or insincere, reduces trust and raises protective barriers. Even though some of it has a positive effect on the relation, as there's always a grain of truth.
If you want to give a sincere compliment, make a stop, and consider why should I point that out? — make the flattery constructive:
"I think you did great during last meeting because you managed to find creative solutions to the problem"
"You make it look so easy! I have trouble writing texts as clearly as you do!"
The key finding here is that while flattery is not the ultimate tool, it's often a prelude to something good. Just don't abuse it.
