is it unrealistic ?

I've become so invested in this that I can't fathom its failure.  My mind has become programmed to the thought that this will last, and I'm unsure if it's because I really want it, or I just need it.  This situation can only end one of two ways, and I've only allowed my thoughts to orbit the positive outcome.  I honestly have no doubts in my recent choices and things have never been better - but I need to stop fooling my naive self and contemplate the less favourable road.  What if ?  What if something changes -because people change and situations arise -  where everything we have discussed and idealised about becomes redundant ?  

I am way past the optimism, and maybe even the pessimism, but realism hasn't helped me in any way.  Yes I'm beginning to gain greater perspective in most things and I've learned to appreciate my surroundings, but what's the point if one day - in an undetermined future - it all ends ?  There is no way I'm ready to even begin to gear up those thoughts again, but the seed has unfortunately been planted.  And unless there is a stronger force that can weed out this negativity, it is only going to grow - bigger and heavily rooted.