Can you only read the al-Fatihah in any prayer and rakaat?

So,sometimes I want to do a sunnah prayer but the problem is that I have no time. Even if I do,it's not very long. So,I always think to myself "Can I do it without reading the extra surah after the al-Fatihah? Is it allowed? Will Allah accept it?". Finally,I've found this website and I hope this will help me.