Flight Changed 2 days in a row

I usually fly for my business twice a month. My connecting flight through ATL has changed the last two days in a row. I was trying to complete a two-day trip to SBN but the delay in the connecting flights makes it impossible to get there at the time I need to. Finally canceled the trip today and received a full refund. Rebooking on United. Loyal Delta customer and Skymiles member. Very frustrating and disappointing.