How careful people have to be when getting carried away even with a good Midda, but they forget the Ikar. They turn into rigid “machines” without a heart. L'havdil, a person who is a big M'dakdek in Halacha can be a big Tzadik (like the Talmidim of the Chazon Ish Zatzal), but he can also lose the “Neshama” of the Mitzvos that he does. Here is a person who is Makpid to daven with lots of Kavana and at Netz, etc., yet he can say: אֱמֶת וֶאֱמוּנָה (which is full of Bitachon and Simcha and Nissim) as a nervous wreck.
It would be K'dai (worthwhile) if he learns some Shaar HaBitachon and feels the kindness and all those miracles that Hashem does before he davens Shachris. Or he reminds himself of his daily Yeshuos and Chasdei Hashem before he says the Haleluka’s B'kol Ram (fervently) with loads of Kavana. This is one of the reasons why Gedolim criticize Frumkeit. You can turn yourself and the people around you into a nervous wreck, with your Shtarka Torah and Tefila.
Sometimes being relaxed and B'simcha is more important, like Dovid who sang loads in thankfulness for his Torah. Sometimes less Torah and Tefila, and less strong Shitos, are a preference. Not to be such an intense Tzadik, and to live and let live.