You have a full-time job and are also doing a part-time evening course. You now find that you cannot continue the course.
Write a letter to the course tutor. In your letter
Describe the situation
Explain why you cannot continue at this time
Say what action you would like to take
Dear Mr. Hoff,
You may have noticed that I have been missing some of your evening classes recently. Even though I enjoy your lesson immensely I work full time at a law firm and as I sometimes work late or because of sheer exhaustion I often cannot attend.
The senior partner in the law firm informed me that I have a certain future there and that I should channel all my energy into work. As I am unable to dedicate the time to my studies I believe it is unwise for me to continue with this course in plumbing.
I would like to focus on my professional career at the moment, so I have decided to put my hobby on hold for the moment. When I have received the promotion I deserve and I have some free time for myself I would like to return to your class and continue where I left off with Drain Management.