How should I make my workout split based on my goals?

I usually do;
Monday; Lower body (calves, hamstrings, glutes and calves)
Tuesday; Upper body, (Tris and bis, shoulders, pecs, traps and lats)
Wednesday; Glutes and abs
Thurdsay; Lowerbody
Friday ; Upper Body
Saturday; Cardio, glutes and abs
Sunday; Rest

Now, I am happy with my upper body. I really only want to maintain it. I can do that easily, and I don't think I'll need to dedicate a day to it. Perhaps I'll just put it with my ab days.
I want to keep progressing on my lower body, but I still need to give those muscles time to rest, so I can't work them every day. If I don't go hard on my upper body, I won't feel like I'm being active enough. How should I set up my split so it ensures I'm still really pushing myself at least four times a week, but without getting any bigger in my arms and back, while still giving my lower body enough time to rest?
How should I make my workout split based on my goals?
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