You probably suck at kissing because you try and toss in too much tongue, or are just overly sloppy in general. Go it slow and nibble the bottom lip a little bit.... practice with your hand.
One has to kiss a person slowly, open mouth using a little bit of tongue. Vary the intensity of your kisses. Kiss on the mouth then move to other sensual areas. Try to be playful, do not kiss too hard or aggressively.