There are many experienced teachers and accomplished yogis on this forum who will provide good advice. Let me touch upon a few aspects.
The growing popularity of Yoga and its sleek marketing spell has created a wrong impression that Yoga, the spiritual path, is easy and anybody can walk it. It is not true. Though each one of us is equally entitled, we are not equally endowed. A legacy of spiritual progress of our past lives, the lifes’s compulsive experiencing due to past karma that is still in balance and a fire in the guts to make it work, all decide the Yoga journey of our present life. Yoga warrants change and that’s not easy. Habits die hard and mind plays all the tricks to justify and preserve most of them.
If you go to a gym and watch someone doing an impossible exercise it is easy to assess the odds against you. But in Yoga, practices like meditation appear deceptively easy. Even when you start practicing, the milestones are subtle and far removed from the physical world we live in. Many beginners in Yoga are driven by high expectations and by a mystique from the folklore. That evaporates very quickly. Fitness is at least one tangible result of asana, but meditation becomes bland over a short period.
There are solutions for a serious students. First, Yoga needs reading, thinking, testing, and validating for each and every aspect of it. This requires Yoga to be taken out of the four walls and beyond “Yoga time” - into one’s normal life. Secondly, Yoga is an applied science. Yoga’s skills of balance, choreographed actions, concentration, meditation etc need to be tried out at every possible opportunity. Thirdly, one has to be innovative. Physical actions, speech, thoughts and desires consume energy. One can use Yoga awareness to economise energy in each one of them.
Collectively, the above brings new quality to life and joy without apparent cause. This motivates. We become ready to change. Then, anytime there is a lull in practice, we will know how to get over it. Like depression, joy also has its multiplier effect. We have to give the initial push and reach that orbit of joy of Yoga.