I need help on hot to stay focus on keepin fit eating healthy and doing exercise programs?

every day i say to my self today i will keep fit do exercise and eat my 5 a day but i never stick to it theres alwase something that just make me eat junk food a few months ago i tried a workout programe witched i did everyday and i was doing brilliantly until 2-3 week in i wouke up one day and i just couldin be botherd and started to eat junk food i thought what a wase of time doing that for 2 weeks when i do exercise i get bored to easy and cant be bothered i seriously need HELP can anyone please help me or any advice on how to stay focus and stuff.