I was asked to write a letter stating why I would be the best for the job. I would like some positive statements to write and I am not great writer so I need some help.

If you have experience in the field, then talk about that. Ex. My four years experience in my previous advertising jobs have prepared my for this position.

Also, talk about your positive characteristics... I will be a positive contribution to your company. I have a great work ethic. I will be punctual, industrious and dedicated. My honesty and loyalty govern all my decisions. I will represent your interests with integrity.

Mention your interest in the field... I have always had a great interest in finance and it's place in our global community. I look forward to this opportunity to grow within such a reputable company.

Just be positive. Do not use a lot of "if you hire me". Speak to them as if you assume that you have the job. Also, put in something specific that shows that you have taken the time to learn a little about the company and it's accomplishments.

Refer to your skills and experience relevant to the job requirements and the company's needs. What benefits are you bringing to this job? Refer to your previous successes and your goals for the future.
Focus on three or four strengths. Good examples include organizational and planning skills, perseverance, persuasive ability and communication skills.