How to speed up my Macbook Pro 15 for editing

Hi there,

I recently began to edit my first short film using the Macbook Pro 15" retina. 2.2ghz 16GB Ram and and I7 Processor. I paid a lot of money for the computer and expected a fast and responsive editing system. Unfortunately when I am editing some HD footage, my computer lags and sometimes completely freezes. I is there a way to either speed up the RAM or CPU to make my editing process more bearable?