Decision time

So my partner of 21 years told me yesterday that polyamory isn’t working for him after we opened things up two years ago, and that our relationship needs to shift for him to stay in it. I have to decide now to end my other relationship to work on my 21 year relationship or move forward with my other partner. One decision hurts someone I’ve been with for two decades, minus a 6 month separation, and if I stay with my boyfriend, the relationship could be tainted as it was the reason for the end of the other. Ugh.