A Little Training Help

I am currently doing a circuit training workout with 30 seconds of rest between each exercise. I currently can only make it through one circuit though I know I should be doing at least two. Is it more important to maintain the low rest periods, and keep the weight up and eventually progress to two circuits? Or should i decrease the weight?

I can do everything with good form and I am hitting my reps but cardiovascularly I am restrained from another circuit. I think I am going to just keep at it, not be a pussy, and eventually get there but I just wanted to check. I really only have fat burning goals at the moment while retaining if not growing muscle, and I do HIIT on my two off days and i do the circuit MWF. Also my lifts are getting easier though I don’t know if I should bump up the weight or wait until after I can do two full circuits.