Transplanting seedlings

I have had the worse time trying to transplant seedlings, its like 3/4 of my plants always die on me 1 or 2 days after I have put them in my garden beds. I really do not know what I am doing wrong. Like the other day I planted some new cabbage in a prepared bed that I have been working and put compost on, and they died on me by the second day. The roots of the cabbage were not very complex, but the stems and the leaves looked healthy enough when I planted them. I don't know if I should put some kind of covering over the plants after I put them in the soil, and if I should what kind of covering should I use? I am so lost and have spent so much money just on plants that won't grow...what am I doing wrong?? elaina Tweet