Should you say how hard something is going to be?

What we're going to do next will be tough/tricky/hard...

Every so often you'll hear the above sentence in a church service or during a ministry activity.

But, I wonder, should you tell people that the next task will be difficult?
Does it help or hinder the chances of the activity running effectively?

Personally, I cringe every time I hear this phrase.

The reason?

The phrase hangs upon its conclusion...

If the person ends the phrase with "but I think you can do it..." Or "but I believe in you..." Then the entire complexion of the instructions change.

Now they are not near impossible obstacles, instead, now you are presented an opportunity.  

Far too many leaders in churches are too pesimistic when it comes to the capabilities of those within and outside of the churches walls, especially the young.

More often than not, people will raise to the task you set them. The worst thing you can do is send the message that you don't think the congregation will be able to rise to the challenge.