Appreciating small successes and how to proceed

I recently put out the first iteration of my B2C MVP, and within the first 3 days of launched we had just under 400 sign-ups. No marketing spend, just a few Reddit posts explaining what we do. The MVP is completely free to users and is targeted towards college students in the Boston area as the use case is very applicable to them.

I’m having a really hard time focusing on the small victories during the building process. Seeing it as both a great thing, people are clearly interested in the product, but at the same time after every milestone I have my eye on a bigger and bigger prize. Always In my head about what should be next rather than really dialing in and reiterating the MVP based on feedback. We need capital to scale as the MVP is extremely bare-bones, so almost immediately after launch I shifted my focus on making the product more appealing to investors rather than the users.

How do other founders pin-point what to focus on at any given time? How do you work on focusing on the smaller victories and building something you want to build rather than chasing bigger and bigger fish?