Take the right things for granted, and don't take the wrong things for granted. If you doubt everything, I doubt you'd be able to maintain a diet or drive a car, or leave the house for that purpose. If you can't see the depths to which that can go, you're operating on the shallow end of doubt.
I take some things for granted at times, but peel back what one would consider obvious and mundane to first principles routinely.
It turns out little of the human world makes much sense, other than in the context of precedent.
The physical world gets weirder yet, as this universe is, to the best of our knowledge and information currently available to us, tautological.
I of course suspend my disbelief for day to day activities, otherwise as you say I would not function, but fundamentally, I believe nothing, not even that I or anything else exists. Descartes was overly glib, apparent thought is no evidence of being, as it requires self-reference.
Some of that may be true, but to affect the world, you nonetheless need to do things. And to do those things, you need to take something for granted, assume something, to complete the task.
That set of things you're willing to take for granted is actually your relevant set of beliefs, because they inform your actions. That's where the important decisions are made, and this is the constant crisis of trying to figure out the right solution with nowhere near enough information.
We can all, in theory, believe that we're wrong about most things, and this is most likely true. But, ultimately, there are things one is willing to do even if they could be wrong about them, because not doing anything is often worse. Sitting in constant doubt is effectively deciding not to participate.
I would rather redefine don't make assumptions but don't doubt - just do to the best of your knowledge. Doubt takes you back , does not put you forward.
* Is there a healthy and an unhealthy kind of self doubt?
* What's the appropriate amount?