E\' facile crederci.

16:21 Jan 24, 2018 

Are you posting this? as I need to close question.

In the meantime, I think you mean one of these???:

"Sure, believing it is easy enough - if you want it."
or
"Sure, believing it is easy enough - if that's what you want."

One of these (with slightly different nuances.)

14:16 Jan 24, 2018 

Yes, this is the sense. For the Certo I would use Sure and would also keep the original punctuation, because it is what gives the text its sarcastic tone.

10:03 Jan 24, 2018 

Do you mean he is saying this in the sense of:

"Believing is easy enough if you want it, of course". ???

09:30 Jan 23, 2018 

I do not think that the sense is "all you need to do is wish for something and you can have it": the character (who by now we have all come to know and love) is wondering whether this is what he really wanted to achieve, and he's trying to convince himself that he made it.
While the two proposed answers are perfectly fine translations, I would go instead with something like "one could almost believe it" because from the rest of the sentence it's pretty clear that he is really unsure he got what he really wanted.