Answer in your head first

Then reveal it.

You laughed properly at something for the first time since the funeral, and then felt sick with guilt. On this lesson, what was actually happening?

You crossed to the restoration side, which is half of grieving and not a lapse in it. The guilt is common and it comes from a belief that the size of your grief is the measure of your love, so any relief looks like a reduction in the love. Nothing about laughing removes anything. In the model, a person who could never cross to that side would be the one who was stuck.