Fixing it is resolved by just closing applications, killing processes, limiting the memory allocated to processes (like SQL Server) or of course you can reboot as a last resort if you really need to. But I'm generally able to get things working again by just cleaning up some of the applications I have runing. As a related side note to this that I may try and cover in more detail later, during the beta, you may want to just kill the noderunner.exe process that is consuming the most memory. I would never do this in production, but then again, you are hopefully not running your entire farm on one 8GB server in production either. The noderunner.exe processes (you will see five if running your whole farm on one server) are used for the different search components - crawl, index, analytics, query, and content processing. The search admin service takes care of restarting a process if it goes down, so it will end up starting a new one to replace it, but it generally takes some time for it to chew up enough memory that it's a problem.
To prevent the noderunner.exe processes from continually eating up memory try this fix to both limit the number of concurrent noderunner.exe threads and also the amount of RAM each noderunner.exe process can consume. Worked for me and my memory usage is now stable without having to continually kill the noderunner.exe processes.