What can you do to ensure that you meet your 4 to 8 lbs a week target? Stick to the plan. Anything else? So what happens if you stick to the plan and you lose 3.5 lbs in a week. Is that failure? What else could you have done? Rather than setting yourself time limited goals which you have no control over whether you meet why not just celebrate every half stone loss? Record it somewhere? Keep track of the positive things that you are achieving. Goals are really important but time limiting them can give you a feeling of failure when everything is actually going well. And feelings of failure can lead to comfort eating. Don't set yourself up for failure by being too hard on yourself.
Good luck hun.