The first real laugh after a death is a strange, guilty miracle. It escapes before you can check it, feels wonderful for three seconds, and then the internal official arrives: how dare you. And later, bigger versions of the same audit - enjoying things again, wanting things again, maybe loving someone again. Each one files the same charge: feeling better is forgetting them.
It isn't, and here's the actual mechanics: grief was never the container of the love. If joy could dilute what they meant to you, it would have to be true that only permanent misery proves love - and nobody who loved you ever wanted that math. The love doesn't shrink when the pain does. It just stops having to carry everything alone.
Think of what they knew of you: your laugh included. The person who loved you built that joy; it's partly made of them. Using it isn't leaving them behind - it's wearing something they gave you.
So laugh when it comes. Want things. Say yes to the trip, the dinner, in time maybe the person. Grief will still visit - joy doesn't cancel the waves, it just refuses to cancel you. Carrying them forward was always going to require somewhere to carry them: a life. Go have the life.