What exactly was the story with Korach? Says Rashi: kina—jealousy! (Elitzafan ben Uziel had just gotten the shteller-job of being nasi-leader of Kehas instead of him.) Wow—what one little bad midda (trait) can do!
So what's the lesson? Be a Dovid, who believed in being "above" bad middos and going always the opposite of one's nature (with a rebbi), like we see time and time again where he is davka tough with "his own" (like Yoav and Avishai), and yet goes out of his way for his "enemies" (like Shaul, Avner, Avshalom, Shimi ben Geira, and Amasa).
While saying all kinds of p'shetlach and explanations on the parsha is great, number-one is to actually internalize the message, and to break those bad middos!
The Gaon (Ehven Sh'leima) says that all bad things that happen to a person chas v'shalom are in fact a direct result of bad middos, and in truth this is exactly what the mishna says in Avos that kina ta'ava v'kavod motzi'in es ha'adam min ha'olam—bad middos pull a person out of the world, chalila, and the Rambam explains (see Madreigas ha'Adam: B'charta B'chaim 6) that all sicknesses and diseases chalila are also all dependent on middos ha'adam—a healthy nefesh makes a healthy guf! Of course Hashem is the Only One running the world, and we're not allowed to chas v'shalom "connect the dots," not for ourselves and not for others ("mi yavo b'sod Hashem", see Rambam in pirush ha'mishnayos la'meseches berachos)—but in any event it comes out from here a great "segula" for all that is good: Tikun hamidos, the perfection of character, overtime! (And ideally with a group of like-minded m'vakshei Hashem ["Seekers of Hashem"], together with a rebbi that you feel understands you all the way.)
