I’m unable to say if it’s generated from the inside or the outside world. Again: I have no words for it. But I'm not saying that love is an experience that cannot be described. I'm rather saying: it cannot be described to those who haven't experienced it, while it's quite useless to describe it to those who have. Let’s try to explain it that way: can we describe a colour to a blind person? I cannot. Do we need to describe a colour to someone who is able to see it? I do not. I may mention it, and this would suffice to be understood. Besides, some discussion is possible about a colour’s shade; then, we solve this discussion by showing the colour. Which, in the case of love, means: we act, we go beyond words.
So, as I see it, behind the word "love" there is a big mystery that cannot be touched by concepts or explanations; yet, those who have experienced that mystery can try to describe it. The weak part of that resides - for me - in the fact that we cannot rely only on words if we hope to describe it effectively, understandably; I think we need also to act consistently with what we say - unless those who are listening have had a similar mysterious experience (and even so, when talking about it, there can be misunderstandings, because such an experience is very personal). To me, love is not an ordinary experience: rather, it’s an extra-ordinary one; and so, I am unable to describe it and explain if fully. And this is what makes it "a mystery".