Simple mistake!

I was at the store yesterday and in a rush, while rushing through the store I grabbed pudding for a dessert I was making and grabbed 'cook and serve' pudding instead of 'instant'! I thought, "Oh well, I can still use it; it will just take a little longer." Well, I cooked the pudding and continued with the recipe, but it did not turn out the same!Let's just say that I had to throw the whole dessert out! I have made this dessert a dozen times and love it, but it is funny that by buying what you think is basically the same thing can change the recipe so much. I don't think I will EVER make that mistake again! I think I should have made time to read the box a little more carefully! haha