First of all..it is good you are starting again..and hugs for you as you do this. As a "second timer" I know how hard this is. I find myself comparing things to when I did Atkins before. I find myself saying "if only I had stuck to this before..." But I try so hard not to do that. That is over and done with and beating yourself up about it isn't going to help. If anything I am more determined this time around because I know what could happen if I am not.
Just make the commitment to start again (which you have done), take that first step and keep going. Don't look back, don't compare. Once you start losing weight and seeing the results of this again, let that be your motivation. Think positive.
Trust me, I am the Queen of negative thinking and self doubt but I really try so hard to just not let myself do that.
Good luck! You can do it!
Jane