You are in full control of your thinking, emotions and attitudes. Your opinions on your ability to lucid dream aren't based on any physical situation or characteristic, but rather the self-defeating thought that you are incapable of lucid dreaming. Convert your attitude into a more positive, adaptive, position. For instance, hold in your mind that belief is the key, also remember that there is nothing setting you apart from the rest of the population that is influencing your ability to dream lucidly (negatively or otherwise). There are many who take months, years even, to get as far as you have in the past weeks. Remember these things and whenever you catch yourself thinking negatively, reinterpret your situation in a different light.
I'm not talking here from some spiritual or philosophical thinking, this is cognitive psychology