Azuc :
I have a 52" LG LED flat screen TV.
My video card is a GTX 770 OC
CPU i5 3570K
8GB of RAM
If I use that tv as a monitor (for playing games from my couch/bed) will it effect their performance? Or have a negative effect on gameplay.
You should be fine if you plan on using it from your bed/couch as you've stated.
Just two things to note about TVs vs monitors that pertain to your situation -
-> TVs have larger pixels. This is better for farther distance viewing but makes close viewing unpleasant.
-> Expect a much slower response time. To compare it to a monitor, it's on average 20ms vs 5ms. If you're used to playing on a tv you won't notice and many people can get away with gaming unless they are going competitive.