Last night you watch the game of thrones, on the other night you watched the walking dead. There is nothing wrong with those movies. What is wrong is your attitude and approach in life. You wanted to quit because you said it is really hard and you can't do it, you said you already give your best and yet you still fail? really did you really give your best? I mean 100 percent pure effort, without procrastination, hesitation and stupid actions? If you really give your best and I can't see holes in your game then I will allow you to quit but if not... then you should keep going.
Early this day, you checked the messages from your facebook, is that giving your best? After that you chat with your friends in skype, you talked about what is the latest gossip in hollywood, is that giving your best? you lie in bed for 7 straight hours because you are making an excuse that you are tired, is that giving your best?
You say you already did your best but you are still alive, because the one who gives his all will also give his life, he will work until he is dead, he will do the impossible things. he will look like crazy, he will test everything. And if you still look alright and you are breathing fine then you haven't give your very best yet.
So keep going, prove them that you are really giving your best, show them that you are dying for your dreams. If you arrived to the point where you almost died and yet you fail then I will allow you to quit. But again, that is not yet giving your best because you are still alive and you can still do something.
The phrase "I already give my best" is a bad excuse. If you can still move and at least try for the very last time then you haven't give your best yet.
You can't quit because it is hard, if it is hard it means you have to keep going, grinding and searching for answers.
You are still doing some actions that are not relevant to your dreams so it only means you are not giving your best. Every action should be related to your dreams and that is the real meaning of giving your best. Giving your best also means giving your life so if you are afraid to die for your dreams, you don't have the right to make an excuse.