Re: the clients/ clients [I would really appreciate comments from the moderators.]
I'd like to point out a possible ambiguity in the sentence.
I work hard for X.
That could mean I had to work hard to obtain X.
I worked hard for my A in math.
I had to spend a lot of time with leads and prospects and selling myself before they signed on to be my clients. I worked hard for my clients.
That could also mean that on their behalf, I work very hard.
When I was on the job, be assured that I worked very hard on behalf of my clients. I worked hard for my clients.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.