You've spent months refining your idea, running the numbers, and laying out a business plan. Now you've turned inspiration into action, shifting into head-down, nose-to-the-grindstone, full-on execution mode. After all, execution is everything.

And then you realize all that focus on execution has caused you to miss at least one of the early warning signs of startup failure. Such as:

1. Potential customers keep saying your product is "really interesting," but they don't actually buy it.

Testing your idea before you actually launch your business is extremely important. Creating a mockup, building a minimum viable product, testing marketing strategies, getting feedback from friends and colleagues and potential customers, and consequently validating your idea is critical.

But no matter how much effort you put into validating your idea before you launch, the proof is always in the sales pudding. Some potential customers will claim they would love to purchase your product but when offered the actual opportunity, will choose not to.

See "interesting" as a sign your product doesn't solve a real problem or meet a real need. And use the moment to ask questions about the customer's actual problem, not just the problem you're trying to solve; and the customer's real pain point and value proposition.

Sometimes a lack of sales is due to marketing -- the wrong messages, poor landing pages, poor calls to action -- but often the problem lies in the product itself.

See "interesting" as a sign you need to revise and adapt your product -- because the only way to know your product truly solves a problem is when customers purchase it.

2. Your runway of funds to support operations will run out in a few months.

If your business is a few months away from being insolvent, with nothing in sight that will extend your runway, only two things will save it: higher revenue or lower costs. (Or, more likely, both.) Sure, you could seek an influx of capital, but unless you also make major changes, all those additional funds will do is postpone the day of reckoning.

Increasing revenue can be accomplished in a number of ways: shifting employees away from future projects and onto sales; reworking pricing strategies; building product bundles; partnering with a competitor.

Decreasing costs is also fairly straightforward. Re-embrace your bootstrapping and cut every unnecessary cost. Except marketing: marketing should never be the first cost you cut. It's almost impossible to save your way to profitability. To survive you'll need to increase revenue. Cut every dollar of unnecessary spending and consider re-allocating some of those funds into marketing and advertising.

Helping potential customers understand the benefits you provide is almost always the one thing you can't afford to not do.

3. You no longer like where you work.

I know that sounds odd. While your business is your baby, building a company is also hard. And stressful. And chaotic. And exhausting. It's natural for some of that early startup excitement to get lost in the day-to-day reality of overcoming constant barriers and challenges -- and dealing with inevitable disappointments.

But just as there's a huge difference between fatigue and burnout, there's a huge difference between not enjoying the present and simply not enjoying the place you work.

In short? You need to love the work. You need to love your vision of the future. You need to love your company.  Or you need to get out. In fact, you owe it to yourself to get out.

Because life is too short to waste time on doing anything less than what inspires, engages, and fulfills you.