I've been together for 5 years with my partner and he's wonderful. He's open but very strong, meaning never sad or down, he feels weaknesses but never complains about them. I feel myself becoming weaker and weaker and very dependent on him. This seems to be hindering my self-development and happiness. I have the impression that these things are related to each other and that it is inherent in the dynamics of our relationship. The conclusion would then be that I have to leave him which I can't even imagine doing. I would like to hear your thoughts.
I see no reason for you to leave your partner if you want to stay with him. But you do need to become less dependent on him; don't give in to the temptation to ask him for help. Do more things yourself and learn to rely on your own capabilities.