Playing the Piano while singing

I started playing the piano while singing when I was in fifth grade. Even though I was just using chords, It was difficult! I remember that it would take twice as long to sing a song with the piano than it did while singing it alone. I am a very great piano player to begin with, but I've improved. I still focus mainly on chords while singing, but I can now incorperate more rythmns while singing, but I still have trouble. It definitely takes practice!