Recording Audio to an External HDD

Hello folks!

Hoping some of you can help me with a question regarding home music studios: I own a late 2011 MacBook Pro and I recently upgraded it to a 480GB SSD and maxed out the RAM to 16GB. This is so my machine can accommodate the various programs I'd like to use to record my own music (Superior Drummer 3, Logic X, etc), but I've heard SSD's are not the best devices to use in this context. Constantly writing to an SSD will decrease it's lifespan, so people recommend recording to an external HDD instead and just use the SSD for the OS and music production software.

If this is true, can anyone tell me how you go about setting this up, or is it simply a case of saving the project to the external HDD whenever I'm concluding a session? I can't imagine it's the latter because if I'm recording a guitar that signal has to be getting written somewhere, and unless I have an external device connected, I can only assume it's the SSD and such processes will relate to my previous concerns.

I'm relatively new to this side of things, so I apologise if I'm looking for obvious answers, but any help/advice/assistance would be greatly appreciated!

Thanks!