Sure: Something I had taken for granted might not even last, as nothing is guaranteed. Have a nice day :)

Hi Angelina, Firstly, the sentence isn't really correct. It's syntax isn't quite right. Despite this, the sentence means this: The speaker is trying to say that he is just accepting, or taking someone and their presence, as a guarantee. In English, when we say 'taking something/someone for granted' we mean that we have become used to their/its presence and no longer show it/them the proper appreciation. In this case, the person she is taking for granted may not even be a guarantee - that is to say, may not be there for much longer. His/her presence is not something that is promised nor will it always be there. Thus - it might not even last. Essentially, the speaker has stopped appreciating something that may not even be there for much longer. It is a sad statement. I hoped this helped, Angelina. Have a nice day, Ash