The surest way to get an unfavourable reference is to let a professor down, yet year after year, students seek out special attention and fail to deliver, often without warning.
- Ensure that promised work-study products are done on time and are accurate, and you express confidence in yourself.
- Check your own work: do not make sloppy mistakes.
- Represent your capabilities and qualities accurately and promptly correct any incorrect impressions.
- Show up when you have promised to help as a volunteer at an academic workshop.
- Follow through to attend an interview or meeting that the professor set up as a favour to you.
If you created more work for the professor, or embarrassed him or her, getting a good reference will depend on that being a complete fluke within a pattern of overall exceptional reliability and quality of your work.
But I was having problems at the time. I didn't mean to be unreliable. It just happened.
Imagine that you were relying on a person to be somewhere at a certain time or to do something they professed the ability to do and had agreed to do by a certain deadline. The person or the work-product are nowhere to be seen. Try these excuses on for size and see how convincing you find them.
I was sick/hung over. I was called in to work extra hours at my (other) job and I needed the money to pay for my car/apartment 10km away from my parents/ski trip, etc. I had to do a household chore for my mom. My girlfriend/boyfriend/coach dumped me. My dog/uncle/computer died. My roommate/neighbour/little sister kept me awake/turned off my alarm clock/became depressed and I had to stay home with him/her. I started to do it but I decided that I was probably not doing it right, so I stopped. My course load was too heavy. I was sad about my marks.
Bottom line: Excuses do not really help your case, and can actually make you seem weaker because they call your problem-solving skills into doubt. Everyone has their challenges. Both grad schools and employers are looking for people who have their challenges under control. Get the help you need to get your situation under control, make amends if appropriate, and repair your reputation by delivering, not by explanation, so that the professor’s most recent impression of you is with your situation under control. If you truly repair your reputation and show you do have it under control, it won’t be an issue.