The below may seem like a mass of contradictions, but... ;-)
I do hold myself to high standards. As in, I expect a lot out of myself. I can be pretty hard on myself (in terms of my how I view myself and interactions with others), and probably don't cut myself enough slack half the time.
But I don't have something innate within me where I feel that I'm going to fail at whatever I do. I have a reasonable amount of confidence in many of my abilities - the 'tangible results' piece.
Beyond tangible stuff, looking more at overall life stuff in the long term...I'm not too worried. Things will work out, even though in the present moment I might be living in a state of confusion or unhappiness or whatever negative emotion. I'm not at all saying that I don't experience despair/anxiety/fear/whatever -- oh, I experience these often. But there must be some deep-seated 'optimism'/'idealism' where I resurface again.
I can only be who I am, and I don't really compare my outward 'successes'/accomplishments against others (although I might be sad or wistful that I operate differently and can't jive or connect easily with many I meet, or might be wistful that life doesn't seem to be as 'easy' or straightforward for me as for many surrounding me); it's always held to an internal standard as far as what I want to achieve for myself. I don't really fret the small stuff, and making mistakes on the little details. I don't mind making a mistake once. If I do it once, ok, fair enough, no biggie. It's if I repeat the same 'mistake', or the same situation occurs repeatedly and I haven't found a 'solution' or resolution to it, then I'll start being hard on myself. Or in terms of my hobby of painting -- I'm incredibly perfectionistic by this point, because I've been doing it for nearly 7 years, so you'd think I'd have it down pat by now. I don't. I still put out really lousy paintings, that put me in really bad moods because I think I shouldn't be making any painting 'mistakes' by this point. ;-)
But there is definitely an element of fear for me in making big life decisions-- and fearing making mistakes with the big stuff --> life direction, job, relationships, etc. I think fear is 'normal' in the sense that anyone will experience it if the person is in any way looking beyond their own comfort zone or way of doing things or existing. But I try not to let the fear rule me - I will take risks and throw myself over the cliff if I feel it'll help me to grow or is something I 'need'. It's not that the fear isn't there...it might be quite powerful in fact - but I sometimes 'ignore' it because I think a greater good will come by me looking past it. For example, right out of college I had the opportunity to go out to Utah for a 5 month job working for a national park. It was June 5ish - I got the offer - I had to provide a response by June 7 on whether I'd be ready/able to be out in Utah by June 16 to start work. You have no idea how scared I was. I was terrified. My heart was thumping. But deep down I *knew* I would regret it if I didn't. I knew I had to go, I wouldn't be able to live with myself if I didn't. So, that was my answer. And 10 days later I was driving cross country to the unknown.

So with the big stuff...I always end up following my gut.
Have I made 'mistakes' when it comes to relationships? My assessments? Jobs I've taken in the past?? Oh, definitely. You have no idea one of the jobs I took the first yr out of college - what a clueless fool I was. But you learn from them too, and you might learn more about yourself through the mistakes than if you didn't make them.