There can be no mystical solution to the problem of existence since any such solution would begin in pure subjectivity and would have to include the outer world as constituted in and by subjectivity and hence would also comport a solution to all the mysteries of the outer world. These latter are simply too vast to be encompassed by any subjective extension of knowing, indeed they would necessarily also include the full objective resolution of the nature of subjectivity as well as so much more. This is something like taking Husserl's crisis of the sciences in the reverse direction and using it to show the limits of consciousness instead of the limits of science. If you start from either direction you reach an impasse and you cannot simultaneously pursue two opposite directions. Any subjective grounding for certainty could only be a shallow foreclosure, and objectively you cannot ground anything at all because there is no conceivable end to the questions. What can you do then? The outer questions are of infinitely greater value but have no end. You can only go whichever way you are able, with humility and keeping your goals modest.