Hi @Avagomum, and welcome to the forum. Congratulations on having finished your treatment.
Give yourself time to process this information. To a lesser or greater extent we are all at risk of recurrence, and we all handle the worry in a different way.
We all have to grieve the loss of innocence that is a diagnosis of breast cancer, and that NED is the best we can hope for. Adjusting to a life where a recurrence is a strong possibility is a shitty thing to have to do, but do it you must. Cry, rage and then take some deep breaths. Uncertainty is part of the human condition. Yours is just more focussed than others.
Have you done everything available to you for your treatment? If not, and you find living with the fear too much, you still have options. If you have, all you can do is be vigilant and trust your medical team.
In the meantime thousands of years of thought has gone into how we cope with the fragility of life! Try a variety of things to help you cope. Mindfulness and meditation teach you that there is only really 'now" and to sit in that as best you can. Being present, seizing the day, that kind of thing. Distraction is good, be it sport, work, a hobby or the company of friends. In the short term the tv, reading or doing a puzzle might help. Focussing on others, something outside yourself, can help keep the fear at a distance.
Fear of recurrence can take over your life. Fear is a useful emotion in that it can protect us from danger. If you are doing all you can to protect yourself from a recurrence then you can tell your fear too f**k off because it is serving no useful purpose at all!. If you get stuck in your fear you might like to see a counsellor for a bit.
Hang in there lovely. Big hug, K xox