I have a Big Problem with Martial Arts!?

Im 18 now and I started Shotokan Karate and Kickboxing at 8 years old!The Kickboxing is going ok but I realy messed up Karate!I use to be lazyy sooo lazy and I was always to lazy to train at home and all that and I missed alot of Gradings in Karate well now I have a second Brown Belt would be black long time ago if I was attending all Gradings.Anyways I copped on now and wana train realy hard but I feel like such an idiot Iv been training for 10 years and theres people in the club who beee training only few years and their a higher grade!Will this mess me up because I want to start training Kung Fu and get realy into Martial Arts am I gettin to old for this now??