What is true is that the journey is not easy, – no journey can be free of any challenges and difficulties, especially where a change of nature is intended. These challenges come from three sources.
The forces of human nature as it has been shaped by our past evolution. As long as man slides down with them they do not resist because man is simply playing to the tune of lower nature. Their play is what constitutes the see-saw game of life slowly changing over millenniums with much waste and catastrophes. The moment one wants to go past them and bring in a new order they resist, creating a sense of struggle rather than darkness.
Then there are cosmic forces whose task is to hinder the advance. They are the dark hostile and adverse forces. They do it so that their reign can continue and rebel against all who seek beauty, truth, love, the breath of divinity in life. They can sometimes create the illusion of darkness and depression by throwing in suggestions of unfitness, guilt, hopelessness. Naturally, if these suggestions are accepted it means one has not enough trust in the Grace. The result is despair. But those who rely on the Grace find that these obstacles not only inevitably yield but even end up making our progress faster and perfection more complete.
The third challenge comes from forces of a higher yet limited order. They seek to hold us fixing the limits of the Light and the Grace. They fix the infinite into rigid dogmas or else lure us into narrower and seemingly easier paths.
None of these can really create any darkness except the hostile. But in the end, even the hostile cannot endure before faith and the Grace. It is only those who rely too much on their own (egoistic) effort who go through such darkness. But for those who rely on the Grace and live in a state of faith and inner surrender, these periods if at all are very short and they do not even feel it as such since held and supported always by Her Grace.
Yoga is a struggle and difficult for those who try to do it relying on their own little strength, which requires tremendous sincerity. But for those who rely upon the Grace, who are open to Her Love through faith, devotion and surrender, the journey is beautiful and delightful on a sweet and sunlit path.