Automatic negative thoughts about different situations

Hello coaches

I have negative thoughts about even normal situations .For eg. I talk over phone to mum and then all of sudden I have thoughts like she is not going to be with me forever.She is healthy and totally fine but I have this fear of loosing my close ones.These thoughts are so automatic it just pops up all of sudden.I don’t like having such negative thoughts at al.I am like do I have to allow such thoughts or develop some bridge thoughts to change it.Is this part of unwanted but can allow thoughts / emotions.