ok so, in this "Perhaps during former years he suffered from the late-discovered unworthiness of one beloved" says "probably in his early years he suffered because he found out the one he loved wasn't worth loving." and when it says" so was disposed to set a greater value on tried worth" it means "he focused to find something better" that's what I got, I hope this helps

Going in cold, I would guess it means that when he was younger, he was *completely^ in love with someone, only to find later in the relationship that that person betrayed/cheated on him and so was unworthy of the trust he had. Now he is older and is perhaps considering a relationship with someone who he may not be *completely* in love with, but someone he knows, from experience, he can trust. And that, perhaps, is now more important to him. That's my take. :D