My tendency that bothers me, and i need help in fixing it.

Whenever i play a champion out of the blue, i do horribly with them, i take a nap because ill most likely be really tilted, and then i say to myself i am a -insert champion name here- main, and then out of nowhere i do really well with that champion, for example with my azir, i normally go like 6/11 with him, i set up 3 rune pages for him, and then i played like a god and my entire team honored me, one of them even gifted me gravelord azir, the tendency that I wanna correct is my inability to play a champion without calling myself a main at that champion, by doing one of the two of the options i have: find someone who i can main, or two, call myself that champions main over and over and over, which i entirely hate, it gives me chills down my back to switch from champ to champ, so what im trying to say is, i wanna find a champion for me, the champion i currentlyhave the most success with has to be either riven or katarina, so from that, i want a champion who feels fast and has alot of mobility, and deals alot of damage, any thoughts??