You Can Do It
On the surface, "You can do it" sounds like simple words of encouragement. But they are so much more than that. If I really know that you can do it, I inform you that yes, indeed, everything you need to accomplish the task is within your grasp. I affirm that the problem is solvable, and that all the tools that you need have been given.
I try to use this with my kids whenever possible.
The Fear of Futility
Your inability to start a task may be more due to not knowing that the task is possible than from the amount of effort it will take or that you might fail.
If I know that a task is possible, my telling you "You can do it" is conveying information. It says that if you try, you will succeed - or at least, you will succeed if you think a little, try a little, and don't give up too easily.
That is usually enough information for my kids to try.
When Success is Unknown
Of course, in life you can't always know for certain that something you are about to try is or is not possible. But the lesson of "You can do it" still lingers.
You remember that there were tasks that you didn't know you could do, and I told you with knowledge that you could. Now, when you are faced with a situation and no one is telling you that you can do it, you may realize that just because you don't know if you can, doesn't mean that you can't.
No, not everything can be done. Sometimes no one will know if you really can do it, or not. Just don't let your uncertainty that it might not be possible stop you from trying. Most of the time, you can do it.