No matter what situation you are in, it is always possible to worry about the future. No matter how well things are going right now, fearful thinking can disturb your happiness and take you away from that which is occurring right now.
There's no right answer to this. There's also no "should". You may have ideas about what you "should" think or feel, and none of those things are related to what is currently happening.
So. The question is, what kind of relationship would you like to create?
Get deep into exploring what kind of relationship you would like to create, and you will find your answers.
Those answers may change over time. It's less about finding the right answer, and more about discovering and making choices. When you do this from a place of relaxation and possibility instead of worry and fear, you will create your advice.
Others will give you real advice and information related to this specific situation, I just wanted to throw this in there as what I guess will be a rather different perspective about this issue on a more general basis. My own 'advice' would be, enjoy what is unfolding now as you never know just how enjoyable the experiences may be, and the idea that because something ends it is not worth having in the first place is, in my view, a life lived in reverse.