pic rel is my bf i somewhat manage to stay on all year:
-track calorie every day
-i like running so i run 2 or 3 times a week, that help being able to eat more
-i stay on my diet in "everyday life" as in if it's just a regular day. If i'm with friends or having a family dinner (or if it's just sunday sometime)I won't care and eat like a pig, feel like this is the most important
-I go on holiday two times a year for a month, so i always feel like i'm dieting for something, but generally after the holiday i stop dieting for a month or two
-sacrificing gains