"The further away into the healing process of grief you are, the less often you think of other people's live events that you can't experience (preggy bumps or announcements, Mother's Day, etc.) as in direct opposition to your broken dreams."
It's like in the beginning of the grief process, you're standing in front of the mirror and you're VERY well aware of what you don't have and so if someone else comes along that gets to experience what you can't experience, the mirror suddenly pops up right in front of you and it naturally breaks your heart in an instant (the feeling of being punched in the gut or below the belt whenever you see that shattered image in the mirror). So even though you're happy for the person who shares the good news or who's going to experience a lovely event, you can't help feeling the pain.
I have this image that the further away you are in your healing process, it's like you're also a lot farther away mentally from that place of pain, from your broken dreams. If you are unwilling to let go, that means that you're still sitting right next to your broken dreams or you're probably even still be holding the broken dreams in your arms. The closer you are with your broken dreams, the harder it is to avoid this "direct opposition" theory.
Hmmm...this is still just a rough theory, but I feel that I'd better write it down anyway.
Grieving is a necessary passage and a difficult transition to finally letting go of sorrow - it is not a permanent rest stop.
Give sorrow words; the grief that does not speak whispers the o'er-fraught heart and bids it break.