Dear sethe,
I think all fears have some basis in reality, which is part of what makes them fearful.
As you said about your beloved pet- 18 years- the thought of the loss of your pet may also have been like anticipatory grief. I don't know what type of pet you had, but I am guessing that at 18 years old it would be natural to worry about losing them, and to recognize somewhere in your mind that that day (unfortunately) is coming.
But I understand, I believe it's the connection in our mind, the conditioning, that definitely plays a role. It is also very salient, what you were 'thinking' or 'doing' when terrible and sorrowful experiences occur, I think we struggle to make sense of it and even somewhere 'explain' it. But the truth is neither did you cause it, not more than you can prevent it by not speaking about it. Not speaking about it really just holds you hostage to feeling it is within your power or responsibilty, and wears you down in the process.
I used to wonder why the most horrible things occurred when I was most happy (and) least prepared to deal with them. I thought that it was somehow 'caused' by my happiness or that at the very least I was unaware of the reality around me. Truth is though, I think that I was just happy, and then unexpected horrible things occurred that no one could have predicted. It did not stop me however from equating it back to something I-did-or-didn't do, nor to fear 'somehow' I would bring sadness to others. And to fear being happy, and certainly not to trust when I was, that disaster wouldn't (won't) follow shortly thereafter.
If nothing else, speaking about it will likely reduce the fear in time and enable you to have more strength to deal with the sorrowful times and more freedom to allow yourself to enjoy the good ones and not live in fear of the next crisis/ loss.
I think too, when we are sensitive and also accustomed to experiences of pain and loss, our thoughts and fears often end up intertwined.
