It is human nature to feel good about accomplishment and certainly there is nothing wrong with this. We acknowledge sobriety dates in the rooms each meeting. It is visual evidence that change in possible.
I attempt to keep an attitude of gratitude on sobriety milestones remembering how my behaviors hurt others and thankful that no longer has to be the case. At 18 months I bought my wife a flavored coffee she likes and went by her work to drop it off. I never mentioned the milestone, she has no idea mostly. I picked up a chip and thanked others for tolerating my nonsensical ramblings.
I must remember where I came from and place a comma after my milestone, not a period. Quiet reflection seems to suffice me, today.