"Thanks for being my inspiration" => 제게 영감이 되어 주셔서 감사합니다. (polite, formal) => 내게 영감이 돼 줘서 고마워. (casual, informal) These are slightly stiff sounding because of 영감(inspiration) which is not used that much. If the context is known, there might be a better way to say it.