Do you find that your boss is inflexible and really does not want to know if you have a sudden emergency such as your dog needs to be taken to the vet or your children are sent home from school because they are ill? Do you dread having to ask for time off because you need to go to an emergency dentist or doctors appointment?
Well if so, then your employer really is not playing fair with you. Life cannot be predicted (which is good really) and that means that there are times when the best employee in the world simply finds that they cannot turn up at their desk or they may have to go home early. This does not make that person a bad employee, just someone who is human.
Most employers will recognise this and be supportive: after all the same has probably happened to them. But if you are having to leave work early every week because the dog has to go to the vet or your children are sent home sick from school, well then your employer has every right to be a little suspicious!
If you do find that your boss is not happy if you have to suddenly take time out then it may be worth offering to make up the time at another point, so if you leave early one day, you could promise to work late the next. Or you could offer to take some work home with you, if this is possible, just to make up the time. This at least demonstrates to your employer and manager that you are respectful of the inconvenience this may cause them and are willing to make amends.
If however, your boss is just not supportive and shows no sign of understanding what life is like, then it is probably better just to cut your losses, sign up with a recruitment agency or get yourself a new job, because if your boss is not going to have a human side, what is the point in working for them?