Same things go for when you're developing trust with someone. It takes time, and it may be slow. However, the results are just as beautiful, because having someone that trusts you can in turn make you feel trusted.

Then, when going down hill it's probably easier and faster, right? 

The same things go for when you're lying. It may be easy for someone you know very well and trust to just lie to you one day, and then lose the trust you had for them in a very quick amount of time.

So the moral of that message is that: 

"Trust takes time, with a beautiful result, but lying can break a trusted bond in a snap of a second".