It's a very healthy thing, in that it saves you from falling for fads, conspiracy theories, and so forth. But if you are doubting things like clockwork, then the safety valve has come to dominate the rest of the system, so to speak.this can become quite burdensome, especially when many entrepreneurs or innovators are untroubled by such considerations. Self-doubt of this kind can inhibit creativity, either due to repetitive fatigue or loss of motivation midway through a project. But by adjusting your perspective, you can make it work in your favor instead of feeling frustrated or depressed. Cultivating patience plays a key role in this.
Helpful tips I have picked up include: rationing your enthusiasm at the early stage so as to avoid regret over sunk costs; treating your loss of interest as a solvable problem with your business model rather than inherent unworthiness; keeping notes and revisiting older ideas regularly; completing small projects (very important, both for motivation and because every big project can be decomposed into smaller ones); giving away simple ideas - sharing creates virtuous circles and builds your social capital; and generally, developing your emotional intelligence.
Your ideas are aspects of yourself, and hesitancy about developing them is often rooted in memories of prior disappointment which you (understandably) have no desire to repeat: losing your enthusiasm is painful, but less so than having it crushed unexpectedly by someone else. 'Rejection therapy' is one way of getting over this - seek out or accept small rejections, and build up a thicker hide. Sharing some of what you can't use is a viable alternative strategy for those who dislike rejection, and if you feel a possessive twinge about some undeveloped idea, then maybe that's because it does have more potential than you were willing to admit during a critical phase.
The fact that you can inventively criticize your own ideas does not mean they are especially flawed. How many ideas do you know that are so perfect as to be beyond criticism? Even things like fire, the wheel and electricity have their downsides. Importantly, if your enthusiasms can be misplaced, so can your criticisms. In other words, just as you may feel you got carried away by the merits of an idea you had yesterday, you can get carried away by your ability to poke holes in it today. Ration your criticisms in the same manner as your enthusiasms, and accept that both are subjective expressions of your own priorities rather than inherent properties of an idea itself.
Lastly, consider whether your critical faculties are telling you to work on something different. Your words remind me of the phrase 'a solution in search of a problem,' and sometimes the world's response to creativity is not rejection but indifference, which is equally dispiriting. Lasers and many other inventions languished unused for many years, so this is nothing to be ashamed of. But if your ideas seem to lack utility, try seeking out problems instead - things that are clearly making life worse for people, but which are agreed to be unavoidable. These domains can be highly lucrative: after all, what are medicine and politics but attempts to mitigate death and taxes? Indeed, many therapists' and consultants' primary skill is that of identifying problems, and distinguishing between symptom and causes.