There are a few ways to control access and visibility to content that may be sensitive in nature.
Option 1: Access to a calendar
For starters, our calendar architecture gives admins and editors the ability to control the access (visibility) to each calendar. If you don't want certain users to be able to see or access content on a particular calendar, then don't give those users a role on that calendar. For more information on calendar access and user roles, give this deep-dive article a read.
Option 2: Make specific content items private
If you just want to hide a specific content item from view, you can toggle the "Private" option on while you are creating your content item (reference photo above), or switch it to private within the Sandbox > Details section. Selecting this option hides the content item from anyone who is not the owner or assigned to the content item.