Okay does it hurt to delete files from my computer if............?

I do have a external hard drive to store them? I just asked this same question almost but got various answers. Some people said that the external hard drives sometimes does not work and you end up losing pics, videos, music etc............now I don't know if I should delete them from my computer to free up my space and that was the whole point in getting the new hard drive. Please help me with this one? I had only 9% space left and now since I have deleted some files I have 22% back. Thanks for all your help!!