Critics are always on the sideline
The moment you decide to change something about your life, you also inadvertently open yourself up to "criticism". It generally doesn't matter what this change is.
Decide to lose some weight? expect comments in the work place, at home, even at gym. Whether it will be someone questioning your form, or commenting about your current weight (I know, like you're not trying to change that right?!).
I realise that this is generally discouraging, mostly because it's meant to be. Consider that most of the criticism comes from bystanders. These come in many forms, my favourite one being the couch potato. Post your recent workout, and these guys are the first jump into the comment section (in most cases, this jump the most exercise they intend to do that day).
People are afraid of change, they will fight to keep the status quo. It way too common to find people being questioned over their protein shake than the weekly alcoholic bender (I know, that protein powder is bad for you right?).
When you get discouraged, you need to remember that you're changing your life, for the better.
Remember why you started.
Always keep a visual record, to track your progress.
Always remember that you're a better than you were yesterday.
Always show up the next day, never quit.