Reboot application without restarting Mac Whenever I try to open Preview on my MacBook, the application doesn't work and I need to force quit it. I would usually restart my Mac to resolve the issue, but I have some code running on the same Mac, which will be done in several days only. Is there anything I can do now? 

What caused Preview to freeze was trying to open several EPS files simultaneously, and whenever I try to open Preview now, I see all those EPS files as currently open (their names are shown if I hover over the Preview icon).
After having opened something that crashes an app, subsequent launches will automatically try to reopen the file that crashed it... &amp; round you go in circles.  

The usual 'first-fix' for this type of issue is to clear the 'history' of what it was trying to open.

Many apps store data in this way, that's how they can set everything back up exactly as you left it, after a reboot, etc.

They live in /Library/Saved Application State/
specifically for Preview, at ~/Library/Saved Application State/com.apple.Preview.savedState the file in here is an Alias - usually they're not so you can usually just delete the specific app's folder &amp; it will recreate it as necessary - but for an Alias it's safer to follow it by right clicking &amp; 'Show Original' which saves the Alias being accidentally broken.  

Delete the contents of the original folder but not the folder itself &amp; your App should launch cleanly.