(Another - bigger - discourager was the process of trying to get your work accepted for publishing.)
This is a big one for me. I know I'm quite a tough critiquer (I'm much tougher in one to ones than on the crits board, too) and I'm very aware of not wanting to squash people. I will usually try to find a positive somewhere. But...!
Sending your work out and getting no response is an absolute killer of confidence. Getting only forms. Getting no feedback to tell you what is good and what is not.
So, I'd rather be tough in a crit and give that person a fighting chance of an acceptance or full readthrough later.
I've done 5 crits this week:
One, to an experienced writer who I'm well used to critting and being critted by, getting a full book readthrough (very slowly - sorry, oh patient one, life is busy...) - they will get my comments warts and all. They're a good enough writer to know what to ignore and they know my writing well and will know when I can be safely be ignored (I stink at description, don't like a slow pace but if I tell you your characterisation is off, it might be relevant.)
One, to another experienced writer, albeit a little less, looking to sub. Their piece was good. It would have been very easy to say nothing - but I felt the opening lacked the wow to attract an agent and I told them so and discussed why and brainstormed what might help. No favours would have been done otherwise.
One to another experienced writer who I know well. It didn't work for me, it had errors. I called it as I seen it knowing they'd prefer that.
Then to two newer writers. One I felt I was over critical of in retrospect and I went back with detail of what I did like in it. The other - they're getting ready to sub, I thought there were some fundamental problems within an otherwise good piece and gave a measured crit.
Now, each person approached me for a crit, either one to one or on a crits board. If you ask me for a crit, you will get one and it will be honest. And I know how hard that can be - I've had crits here that brought me to tears, big soft eejit that I am. But I do no one any favours if I don't provide what they asked for: a critical analysis. Because it is better here and now than from the pros.