Wouldn't be nicer if a Single SharePoint Control does the job of authentication and authorization. Yes , We do have a Control called "SPSecurityTrimmedControl" . This control can be placed automatically by adding SecurityTrim snippet from the Design Manager of SharePoint 2013.
SecurityTrim snippet can be inserted in either Master Pages or Page Layout to display the content (static or dynamic) based on the User Permissions.
Below are the scenarios Where SecurityTrim snippet can be of very useful.
Content Search Web Part, to display the current logged-in user's documents.
List view web part to check recently modified documents.
Content by Search web part, displays non-authenticated visitors.