You answered your own question. you were living in your current reality, feeling that he is not with you and that brought up emotions and fears. 
Be patient with yourself, just because one day hasn't been going the way that your days have been going and you are not in the best feeling place does not mean your manifestation won't come. It is important to acknowledge good with the not so high feeling emotions as well. 
If visualizing isn't working for you then find something that makes you feel better. Write in a journal, do some meditation and get back into that feeling place. Know that the negative feelings will pass as well and you will get back to the good feeling place that you felt like yesterday. 

I'm confused. You want a relationship with this guy, you applied LoA, but then you noticed it's been a month without results so you start to miss him. And now you've let go. What exactly did you let go of? What does letting go mean to you?

I have these days now. This month it's the hardest for me. But really, as everybody say, time is so relative.
Also, I wrote this to Sanshi few times, some beautiful manifestations I had when I was sooooo sad. I think that MAYBE that kind of sadness is kind of letting go of pressure. If this is logic to someone?!

I know the feeling. We all have DAYS.
The best feeling is when you can say- I'm ok. I'm letting everything to Universe and I believe.
And we can do it!!!

Yeeeah! You see! Everything is going to be ok!!!