Someone has pretty much already touched on most of the advice, but to re-iterate:
-Don't be afraid to lose.
-Practice practice practice. You should get to the point where you just execute a combo without really thinking about it. So basically you need to practice to the point where muscle memory kicks in.
-Your 'favorite' character isn't necessarily your best character, so you may have to suck it up and use someone else if you really want to be competitive. For example, my favorite character in "Injustice" was Solomun Grundy since, well, he's a giant immortal super-strong Zombie, and that's awesome. Unfortunately, I'm awful with grappling characters, so while he was certainly my favorite character, he definitely wasn't my best character.
-Don't be afraid to lose.
-Practice practice practice. You should get to the point where you just execute a combo without really thinking about it. So basically you need to practice to the point where muscle memory kicks in.
-Your 'favorite' character isn't necessarily your best character, so you may have to suck it up and use someone else if you really want to be competitive. For example, my favorite character in "Injustice" was Solomun Grundy since, well, he's a giant immortal super-strong Zombie, and that's awesome. Unfortunately, I'm awful with grappling characters, so while he was certainly my favorite character, he definitely wasn't my best character.