The biggest indicator of a startup’s failure isn’t product-market fit. It is a lack of customers. My startup has already pivoted several times in the past year and eventually narrowed the focus to something that works.

How did we realize we were finally onto the right idea? Customers. Big, important customers suddenly began to show interest in what we were offering. We had a lot of interest early on, but very little follow-through beyond the first few conversations. Fashion, particularly, is an archaic industry with a lot of paperwork and very little technology happening behind the scenes. Most of the ordering takes place via Excel worksheets and Google docs. And if you’re really unlucky, fax machines may even be involved. Getting customers to adopt new technologies under these circumstances isn’t just difficult—it’s almost impossible, especially in the short period of time given to tech startups to show traction.

The key, then, is to determine how long is too long to wait it out. What is the difference between patience and negligence?

See also: Why it Might Be Time for You to Leave Your Startup

Listen to your customers. As a startup founder, part of the problem that you are trying to solve must instill some sense of urgency on the customer’s behalf. Why should your customer start using your product right now instead of tomorrow or next year? What value can you offer this very second that a competitor cannot? Demonstrating this in black and white to your customer base will set you up for success.

If a customer cannot immediately determine what you can do for them, they will be unlikely to use your services, or will delay using them long enough to forget about them completely. Without the support of your user base, your startup will likely run into long-term trouble. Every successful startup has been able to quickly solve a clear problem for their customers.

Uber will get you a car right now. Minibar can get you a bottle of liquor right now. Postmates can deliver virtually anything to your door right now.

Each one of these companies can provide tangible value to their user base within minutes of engagement, which is why they are so successful. The other important thing to note here is that the value proposition is easy to understand. Communication about your offering must also be succinct. If it’s difficult to explain what you do, then create a video clip or infographic. I have found both to be equally effective with investors as well as customers.

In the event that you cannot incentivize your potential customers to pay for your services today, it’s time to drop your startup idea and find something else that works. There is no shame in starting over. There is only shame in giving up.