If you dont want segs dont do the missions that give them. Know which interactives give segs and when, dont do e-missions for segs, and stay away from Derilect Motherships and Super Novas. Once you have the segs you cant get rid of them unless you get attacked a ton so deside how many you need.
I made the same mistakes. End up with too much segments and getting attacked left, right and center. I don't mind if they take away my segs, but they destroyed my ships as well.
Now I learned. I tuck away my ships, put them in reserve, and then I let them attack me. Actually I welcome their attacks now as long as they take away those segments.