Is this something you can 100% control. SImilar to saying "to have a good relationship, the key to success is enjoying it" Not all factors will allow for enjoyment. I love maths, I love helping people but to say I enjoy a low ability/poorly behaved year 10 group who are not doing a GCSE for 3 last periods per week would be a fallacy. The majority of the lesson is a case of containing a situation with many volatile pupils who know they are not going to get a GCSE. Their math ability is too low to do too many rich tasks and 4 hours a week with them soon leads to a saturation in terms of motivating fun lessons. I agree you have to enjoy your job but it doesn't make you a good teacher or a bad one if you don't enjoy parts of it. A good teacher in this situation is someone who can keep pupils seated, maintaining some discipline and keeping these pupils out of more productive classes. Learning is a slow and very few teachers want them, good or bad.