Without genuine interest, you won’t be able to maintain consistency. If you want your work to feel like play, you must have a genuine interest.
If you are working in a domain that is not your area of interest, then you need to force yourself to learn more about that domain in depth, you may unlock your interest in that domain if even after understanding a domain in-depth, you are not getting any interest to continue then move to a domain which you feel that you are interested.
You will know that you have a genuine interest and later will find love in your work, only after certain years of experience because you will develop a great amount of knowledge over the period.