It's hard to comment on things like this because each program has its own requirements for what they need in the letter. These should be specified on the application or by the program/department you are applying to.
Also, be careful of copying sentences suggested by others on the internet.
Some general comments:
do not repeat words/phrases
avoid abstract words and obvious/generalized conclusions: they know you want a degree to get a job; everyone believes they'll contribute; I want to improve my Swedish in the near future, but I probably wont... do you have concrete plan of action on learning the languages? -- provide concrete details and goals
be as concrete as possible
don't use cliches -- everyone says that "your program meets my goals" -- how? what goals? specifics?; also avoid "I am confident", maybe you are but they aren't
Why do you want to go to this particular program? Needs details. They only have "interest" in African Studies? Or do they have some unique resources? Is some expert in the field teaching there? Etc.
You are trying to stand out in the sea of applications. They've seen every cliche and vague generality in the book. Concrete and specific things stand out and also show that you're prepared and serious.
- For Teachers