I believe that good critique partners are absolutely vital to the writing process. A good critique partner gives valuable insights into improving your manuscript, and will also cheer you on as you go on your writing journey.
When I figured out that I needed critique partners to improve my writing (side note: sometimes I look at 2013 Kara and slowly shake my head at her nonsense), I was delighted to find that two women I already knew were writers, and they were interested in forming a critique group! We were all kind of newbs at the offering feedback part of writing, but we dove into it anyway.
At the beginning of that summer, I let my new CPs know that I was going to pursue publication, and I wanted their help getting my book into shape. They both agreed to read for me, so I sent the book on.
And then I waited. For almost three months. One of the women suggested that we add new people to our critique group and move it online. I said I would be okay with that, but if we were going to invite new people, we should be clear on when we expected people to get back to us so that no one got upset, because my feelings were hurt that neither of them had said anything about my book the whole summer.
Now, they both had a lot going on that summer. They were scheduled things that we all knew were going to happen. But they had agreed to read in spite of that, and it bothered me that neither of them had even said so much as "Hey, sorry I haven't gotten to this yet."
One CP apologized, read the book within a week, and returned notes that were very helpful (including pointing out that I wasn't doing my em dashes correctly, which was great because I had no idea that em dashes and hyphens were different!). We're still friends to this day, and I still value her input on my work.
The other got snippy, unfriended me on Facebook, and hasn't spoken to me since even though we live in the same small town.
I hope you take away a number of things from this story. One: if you are unhappy with something in your CP relationship, speak up promptly. Don't let it fester for months. You'll know which CPs are worth keeping based on how they respond. Two: if you find that you've screwed up? Apologize and make it right. If your CP forgives you and can still take your critique without getting defensive, then you guys are a good match. And finally, clear communication and honesty are crucial to a good CP relationship.