Most people when starting a lifestyle change program want to go all in. They want to change all bad habits at once and start an aggressive workout program immediately. It makes sense, complete flip to "healthy living" as soon as possible. The problem is not only is this impossible mentally, your body does not like change so it will also turn on you.
The key here is to start slowly, change one habit at a time, pick a workout program that gradually ramps up, and listen to your body. The hardest part of that is LISTEN TO YOUR BODY! Most likely at some point you are going to feel run down and tired. Everything tells you to back off and rest, but mentally we have a schedule to keep and want to fight through. The reality is rest is important and it is ok to skip a workout every now and then to recover.
You need to come to terms with the fact that lifestyle change is a marathon and not a sprint. If you go to fast you will burn out and possibly become injured. Resting allows your body to recover and become stronger. So don't be upset
when you have to skip a training day because you are tired. It will make you stronger in the long run!