Weights loss advice

So I'm really ready to start losing weight and getting healthier. I am 5'10 and 265 pounds. My problem is Everytime I start trying to lose weight I do good for a bit then mess up and completely get thrown off. What do you guys do to battle that? And what are some tips for battling the cravings? Chips and salty foods are my weakness. Also I'm really on the go and work 12-24hr days sitting in an ambulance so I struggle with meal prep. Any advice, tips, and tricks would be so appreciated!