When I feel grateful about someone, I sometimes use the phrase
keep up the good work
after I have thanked them.
I only use this when my feeling is that he or she:
- is doing good things and/or
- has just been doing a good thing.
However, I sometimes worry when he or she:
- has been working for free, so they are somehow sacrificing themselves and/or
- has been doing something good just because I asked them as a service.
In any or both of the latter two cases, is it still a good phrase to use? Or can it be hurting?
My worry is that, when understood litteraly and not like an idiom, this phrase actually means:
I want you to keep on.
Which sounds rude to me if the person has been kind enough to volunteer. What I actually mean is:
I am glad that you did/are doing this. There should be more and more of people like you in the world.
Is my feeling correct?
Is this phrase idiomatic enough to be simply understood as "thank you", or should I stop using it in the last two cases?
If so, what would be an alternative?