Well for me, the "difficulties starting out" didn't really happen till I'd been taking weekly classes for 5 months and attended my first white tantric.
I sort of stumbled onto Kundalini yoga at a "Tennis Club/Gym" where I was teaching weekly bellydance classes. I loved it from the first day, felt like I'd come home or something. I really enjoyed having music (mantras) to move in time with and the teacher often did a gong meditation which undoubtly moved things around.
And even though I'd been practicing hatha yoga for years, I'd never gotten into the bhandas or breath of fire. I was hooked on the rush if it all.
Maybe my previous meditation experience, silent sufi meditation, had already cleared up a few layers of the painful stuff.
I did my first white tantra with my teacher. In itself,it was a lovely experience, almost all the meditations were to the Gurudass's version of Adi Shakti. But wow, starting the next day I was sick and for 3 weeks, did some heavy duty clearing out, fever, cold, sore throat, you name it. It also literally forced me to quite smoking, I physically couldn't.
But I believe, like in any spiritual practice, things go in phases or cycles. So there can be difficulties or not anytime we keep up with our practice.