Now that you've put yourself out there and asked for other's critical feedback, it's time to dive into those first edits you've received from your first editor.
The first time round, making yourself vulnerable by letting another read and pick apart your work is going to hurt just a little bit. It will start to get easier each new time you do it...sort of. Maybe it's just that you get more used to it but think of it as getting tougher skin and as a process of getting stronger. It will make it more bearable.
Give yourself a little pep talk before you open your editor's notes. Know that it is the act of your writing that you're even able to receive this critique in the first place and that in itself is a beautiful thing. Now, take a deep breath and open up that doc and get to reading. Let yourself take the time to read each note your editor has written, allowing each suggestion to sink in so your brain can begin to work out how to approach these pieces of feedback.
After you have read through all of the notes and red marks, which may take you multiple days, take a step back and look at it as a whole. What are the biggest areas for change and sprucing? Maybe your editor is so kickass that they spelled this out for you. If not, find the biggest holes that need to be filled and let your mind begin to work out those problems.
For me, one of my big pieces of work is the back stories of each character. I am taking the time to write out the stories of where these characters have come from and what has happened to them to put them into this story. None of this may actually even be put into my story, but it will make my character's motives more clear to me so that I can more properly express that throughout the story. This is my first broader change that needs to be made to my story, but I have a few other big ones I'll be tackling after that.
This is a hard, painful process, but it is going to be worth it. If you let your story keep its holes with weak character motives, what would be the point? You're going to have to put just as much of you, if not more, into this editing process as you did actually writing it for it to turn into something beautiful. You can do this.