Ivf with donor eggs

We just found out today our first cycle with donor eggs was unsuccessful. :( despite the embryologist saying our day 5 transfer with blasts gave us wonderful chances as uterus lining and the eggs looked awesome.. Very upsetting to say the least as we have have negative results 6 times previously ( 4 IUI's and 2 ivf cycles with my own eggs ). It's hard to remain positive some days. I'm 39 so my egg quality is poor; we had a ruptured ectopic in 2012 and an early miscarriage before we started the ivf journey... We still have 4 frozen blasts which we will probably try, when we can in a few months time. I struggle with when do you stop trying... :(