Overclocking can always be scary at first but rest-assure that you cannot damage your card unless you over-volt your GPU which at this point msi afterburner (the app I assume you're using) has disabled this feature. You can use GPU stress testing applications like Unigine's Siperposition application to see if your GPU runs stable during full load tests. If the application crashes or you get any errors then that's how you know you've over-exceeded your cards limits.
If you do get any application crashes after overclocking don't be worried as the card will not suffer any damage. Just reset the core and memory clocks to default and try again. You may also raise the overall power-draw (the second top option in MSI afterburner, this ups the WATTAGE, not the VOLTAGE) to 110% as the card's VBIOS (your GPU's firmware) will know it's safety power limits and pull more power but to a safe level.
Also note that the better you keep your card cool (64c or below) the best and more stable performance OC you can achieve. So keep an eye on how far you can push your card depending on your avg GPU temps during gameplay.
tl;dr
Overclocking doesn't essentially damage the card, only changing the VOLTAGE will cause long-term affects.