Is a Cover Letter Important with Your CV to Get a Job?

I applied for a position I was particularly interested in. I forgot to attach a cover letter with the resume. Now, my friends are saying it is a significant document and now I am really worried. A cover letter presents one's interest for the job opportunity and explains to the employer why you are appropriate for the role. They recommend I get a top cover letter writing services from toresume.ca.
I thought that my CV was strong enough, but now I am confused as to whether I missed an opportunity to stand out. Have any of you ever submitted a CV without a cover letter? Do you think that it affected your chances of getting hired? I would love to hear your experiences and any advice you have!