Well, first, (not to be too techcnical) I did not construct my belief system...it may be a fair place to start, but one must be prepared to let go of that at some point. The system is far bigger than I can construct. I can participate in it though.
And more to the point....I started out with a glimpse of assurance, and it became an inner "yes" that was both of the mind and of the heart. For me it was enough for a leap of faith. In the years that have followed, I have come across many other assurances that interlink and amplify each other in ways I could never concoct. Some were totally out of the blue. Again, these have been both of the intellect and of the heart.
Still, full and complete assurance implies a degree of control that I suspect I will never possess (not do I need to). No matter how far one goes, faith is still a very core principle. Thing is, the arrangement really works out much better this way, primarily due to the inherent vastness of it all. It is not something that we ever possess entirely.