If you don’t pray the Sunnah prayers, you are not sinful but you shouldn’t allow Satan to fool you into not praying it because you feel more Khusho’oa. You should know that praying the Sunnah would increase your Iman and it wouldn’t reduce it.

I wonder, when I sometimes missed a prayer or I have sinned, I feel so depressed and when I pray I shiver whenever I recite or hear about Hellfire or good news about Jannah.Its like going from my spine down to my feet.does this mean I attained taqwa, because before I use to watch porn, but not now, now i just shake it off because I am ashamed of Allah seeing me in this state, and I don’t want to please shaytaan, I love praying but I wonder am I sinful for leaving the Sunnah temporarily until I become stronger and performing the Sunnah to, just so I adapt my body to enjoy more, I use to do those, 2 rakaa’at before fajr, also pray qiyaam’ul layl, before I get too tired and I can not focus but when I only pray the Fardh I enjoy more, and I still have khushoo and whenever I pray qiyaam’ul layl then my day become so much better, no one should ever abandon this prayer because it contains so many virtues. That was my question.