"How do you write if you have a perfectionist personality flaw?"

I saw this question asked on a forum for erotica writers yesterday, but there was more to the question than that:

I try and then every time I get to about a thousand words I get this overwhelming feeling that this thing I'm writing sucks, that I have no talent or original ideas.

But another part of me just wants to write to practice and get better.

Do you guys just tell yourself "I'm going to write X words today, and it doesn't matter if it's pure crap"? How do you let go of inhibitions?

This was a lot more than one question. I had to untangle it:

How do you let go of inhibitions?

I consider myself a perfectionist, and the way I get past inhibitions about my writing is simple: I write, though this is a multi-part process (see below).

Sometimes that means working on a different piece; I've barely touched one of my half-finished stories in 18 months. Why? Because it intimidates me; I like it so much that I'm afraid I will somehow fail it with additions that might not be up to the same standard. This is a singular experience for me and may not translate to others, but it's one reason among many we might come up with to avoid writing, all of which can be overcome.

After setting that piece aside, I tried editing the writing of others, helping them tighten and make readable what had previously been a confused but promising muddle, then realized this wasn't helping me write, in fact it put me into an unproductive, self-reinforcing funk. Several months later I was inspired by a brief encounter. I started writing something new for a contest, the story tumbled out, and last week that book became my first published novel. Now I have four works in progress, all of which I (usually) like. That's honestly too many, but one is too few.

Do you guys just tell yourself "I'm going to write X words today, ...

That might work for others but would set me up for disappointment. Some days I write less, sometimes more, sometimes none, and sometimes a lot. I might pay attention to average words per day, but as my books get farther along, the writing slows down, so that would also be counterproductive.

I try and then every time I get to about a thousand words I get this overwhelming feeling that this thing I'm writing sucks

Me too, but I also know that the next day, with a little distance, I might think the same writing is pretty good and can be made better.

[I get this overwhelming feeling] that I have no talent or original ideas.

Whether your ideas are original or not shouldn't be the concern. Your characters, their interactions, your language, your voice, and the way you tell your story should feel original, to you and others. That can only come from you. Ideas can come from anywhere.

Ask yourself: 'what could improve what I've written?' Make it about the work and not about yourself.

another part of me just wants to write to practice and get better

You titled this post "How do you write if you have a perfectionist personality flaw?" And you just answered your own question as neatly and succinctly as anyone could.

I maintain that perfectionism is not a personality flaw, it's an asset. Not necessarily to productivity, but certainly to quality.

I found a typo in my just-published novel on reading it in bound, printed form for the first time. The perfectionist in me cringed. But even the perfectionist in me can live with one typo in 41,000+ words.

For what it's worth, here's how my writing routine goes:
1. I review some of what I wrote previously, ideally to the point where I'm ready to continue the story.
2. I read someone else's good work for 10-30 minutes.
3. I take a break, maybe take a walk, and let the wordstorm settle.
4. I start writing, and go 'til I don't want to any longer that day. I do not spend time being critical of my writing as it emerges; that's for tomorrow's editing.
5. I let ideas come to me when I'm not writing, though sometimes I have to take notes. On walks, in the shower, in bed, thoughts can come anywhere, any time.

Good fortune.