Since I was young, I have always kept cards, letters and other mementos that celebrate milestones in my life. For years, I have used a journal like the one pictured above to house all types of things. I purchased this Kate Spade journal from Papyrus. Not only is it beautiful, but it is functional. I regularly pull this journal off my bookshelf and review the contents. It is fun to look at notes my children have written to me over the years. And to read cards my husband has given me for various holidays and anniversaries. And I even have some older photos of the kids thrown in. I imagine a time once I'm no longer on this earth, that my kids will find these journals (I have many of them) and will enjoy reminiscing about their mom and her life. I think that is one of the great things about paper and handwritten notes...you can keep them for future generations to read and enjoy.
If you decide to try a keepsake journal, my biggest piece of advice is to put the keepsake item in the journal quickly after receiving it. That way it won't get lost.