Would you be ok knowing your partner is hiding part of their past from you?

Early on my boyfriend told me he did something in his past and he is afraid to tell me because it could distort how I view him. He said he told someone in the past and that person never looked at him the same aging. I am all for people not having to tell all their business. But I feel like it's something that I should know... I don't want to be together for 10 - 20 years and be dropped with something crazy. It's been almost 2 years now and it bothers me a lot. I asked him if he hurt anyone and he said no. I even told him if no one was hurt I can pretty much accept whatever it is. But he refuses... whatever he did he went to therapy for and said it sends him "To a dark place" If he thinks about it.

Would you be ok knowing your partner is hiding part of their past from you?
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