Those who strive for success also take a risk: failure. However, the evaluation of success and failure is a matter of perspective. If you're interested, you can read my personal, perhaps somewhat unconventional, views on the subject here.
Do you want proof that your project will succeed? Sure, we'd all like that. Forget it, there's no guarantee of success. Success is success because it follows action. Proving success before taking action turns the cause-and-effect principle on its head.
Those who don't act achieve no success, because the very foundation of success—action—is still missing. This action requires a stake, which we risk for the hoped-for gain. This is essentially our wager. We can, for example, bet time, money, knowledge, health, reputation, or family happiness on the project's success. The size of the stake, and thus the risk, is usually determined by the strength of the positive feelings we associate with the desired project success.
These emotional expectations are in turn driven by needs, the fulfillment of which sets our hormones in motion. This state of success-induced euphoria is what we call a sense of accomplishment. The driving needs can vary widely: recognition, status, knowledge acquisition, etc.
Interim conclusion: Without the expectation of need fulfillment, there is no effort; no effort without risk; without effort, no action; and without action, no sense of accomplishment. That's how it is.
Unfortunately, projects do sometimes fail. Then we're disappointed because our efforts seem to have been wasted. This understandable despondency arises only because we measure success through the lens of our initial expectations.
Now it's worthwhile to look at the success metric from a new perspective. To do this, we gather, regardless of initial expectations, all the positive aspects of the project. Then we consciously consider what we have unexpectedly gained from our efforts. There's much to discover: for example, insights and experiences that will help us be more successful in the future. If this assessment is negative, we should reflect.
This situation helps us to ask ourselves critically: Was the project worth the effort? Why wasn't it worth more effort to me? How much effort am I willing to give in the future? The answers often set an important course for career development or future life planning. In this way, failure can ultimately provide a fair return on our efforts. It could even lead to an insight that is far more valuable than the effort itself.
Conclusion: Look closely when you're plagued by failure! Perhaps an unexpected stroke of luck is hidden behind it.

Remember: If you're in over your head,
This doesn't have to be a catastrophe. (Image: Peter Siwon)
I welcome your suggestions and feedback at denkanstoss@microconsult.de.