If it's suffering, you're pushing too hard. I think that's the challenging thing for beginners to understand. At worst you should be bored, most days. You don't really need to push into uncomfortable territory until you've got some regular volume and want to improve race performance.
Maybe I'm doing it wrong, but for me there certainly was (is) a mental hurdle to get over. When I first seriously started exercising I think it probably took 6 or so months of 3-4x per week before I began looking forward to it. Even after years of training, I still will battle with myself a bit before heading to my muay thai gym or heading out for a run.
There are different approaches to learning how to run. I picked the suffering approach, where I'd push myself to log miles even though I was gasping at the end. Now that I'm an experienced runner prepping for a 50 miler, I agree about training yourself to boredom.
