I think I got that card when my dad died last month. Its a nice sentiment, thanks.
When you lose someone so close that they have been a part of you, there are more complicated issues than lovely aphorisms can address, though they have their part in retraining the brain and heart to desensitize.
It isn't simply the memories that are involved, there is the ingrained expectation of interaction. The little things you think to share because your mind hasn't come to terms with the permanence of the loss. If one more person says "At least he isn't in any more pain" or "He's in a better place" I will probably barf on them.
Its not the sadness or pain, its the hole blown in your life that must be filled. Only time will do that.