First thing you must do is to understand from your oncologist the chances of recurrence. Also the chances of cure at that time and possible treatment options. Understanding these things will drive away accumulated fears from the mind. Some will be at a high risk and some at low risk. The aim of follow up is to detect the recurrence as early as possible and treat it.
There is no need to get scared of it but be cautious of it. The fear of recurrence haunts the mind which needs to be addressed. By worrying about it you cannot prevent it. Please look out for same swelling, or symptoms and report to treating oncologist.
Be on a regular follow up with your oncologist. Whatever tests have been recommended please have them and show them in time t your oncologist.
Follow the same precautions of diet, weight management, adequate exercise as for prevention of cancer.