This is a question I've struggled with myself for a lifetime. Only in the past three or four years have I made really major headway in feeling more confident. I have found a few things that help: talking to myself--out loud. (Best done when alone, for obvious reasons, or at least out of earshot). "You can do this--of course you can. Why would there even be a question about it, you are infinitely capable of doing this," I have told myself, and strangely, have tended to listen. Reminds me of the song in The King and I": "Whenever I feel afraid, I hold my head erect and whistle a happy tune, and no one will suspect I'm afraid"--or, in other words, "Acting! Thank you!" ;-) And it never hurts to remind yourself just why you deserve to feel confident. You have an engineering degree, right, Marc? That means you are smarter than perhaps 98% of the people on the planet. That doesn't make you "better"; it makes you "better able to think/analyze/observe/cope" whatever. I think a lot of not feeling confident has to do with feeling, on some level, that we don't deserve to feel confident--that we have not done anything worthy of feeling confident about, or, if we did, it was short-lived and we shouldn't continue feeling worthy for more than five minutes. My parent were well-intentioned, but they should have spent a lot more time telling me I could do and be anything I wanted, and a lot less time saying, "don't toot your own horn." Toot it! Toot it loud and toot it proud! (yes, I'm snickering, too--humor is helpful, as well ;-)) And if you want to feel "yellow, " think yellow. You deserve to be any color you like. When you accept that, intrinsically, you will demonstrate it, extrinsically.