When you feel like giving up, give yourself another month for your changes to start having an impact on your life. And don't dismiss the tiny differences, such as being less out of breath, these are indications of something much larger. Setting realistic goals is particularly important in adopting an exercise regimen. A person's body takes time to gain cardiovascular strength, muscle, and flexibility. Rushing this process will lead to injury.
Many people injure themselves just when they are getting started.
Intersperse hard days with rest days so that your body has a chance to heal, and you have a chance to push yourself without getting hurt. It is equally as important to make a plan that is convenient to you, and that doesn't demand of you that you make the decision to commit again and again everyday. Don't make a plan that is bound to fail. If your resolution is to drink less alcohol, make it convenient for yourself by making sure you have something else in the house to drink. If you want to workout more often, find a gym that is on the your way home, and choose an exercise that doesn't require a lot of equipment at first, like walking.