Hi, Eliza.
Yes, it is perfectly normal.
When my husband died suddenly last year at only 37, I thought I’d never get over the pain, but gradually, day by day, it went away until I woke up one morning, and not unlike you describe, I felt… GOOD! It’s not wrong. You have to go on living. There will still be days of indescribable sadness and days where you don’t want to get out of bed. The best thing you can do is be kind to yourself. Talk to yourself like you would a good friend. Living your life is not an insult to his memory. Giving up is. It will be a bit of a roller-coaster, at first. Then, those bad days will become fewer and further between. Personally I don’t find birthdays and holidays tough. For me, it’s the mundane things we used to do together that gut me. For instance, shopping for groceries, or taking my son to Scouts. I eventually had to change where my family did both, because I invariably always found myself looking for him even though logically I knew he wasn’t there.
This is not a plateau; it’s a progressive a step up.
Eliza, you are going to be OK. I promise.