You must understand the background.
If you have nothing to hide, you have nothing to fear.
That's actually not the point of deeper security vetting. Deep security vetting is not a pass/fail process (although the data contributes to a final decision), it is a risk assessment that is actually in your interest.
Such an assessment seeks to discover where an adversary might seek to coerce or pressure you into cooperating, and plan accordingly. It means that some work may be a personal risk to you, or that you may be very suited to some work because you do not have a weak spot there.