Your dilemma is quite common when you hear new aspects about yourself from others.
Self-Evaluation: Capabilities and Interests
First and foremost, I suggest evaluating yourself on your own: (1) Capabilities and (2) Interests. If you find a particular field that satisfies or concurs with both aspects, just go for it. The circumstances and limitations are something that one can handle along the way. What finally matters is self-satisfaction.
I have seen many people being advised in good faith and absolutely with no malintent about aspects that take only some of the strengths or limitations of the person involved—for the simple reason that they were exposed to only those aspects of the individual. It's only the individual concerned who would know in detail his or her overall strengths and limitations.
Decision-Making: Considering Others' Inputs
While taking others' inputs into consideration, the final decision has to be yours, since it's your life and career. Quite often, people tend to pass the blame onto others' advice if things don't work out the way they were intended to—when they always had an option not to take the advice.
Discipline Across Fields
Coming to the points you mentioned, which field, domain, or function doesn't need discipline—except that the parameters could vary from function to function? One small example: My time discipline and punctuality will have to be very good if I am working in shifts than if I was in a general shift—since in a shift, apart from the work waiting for me, I will also have to relieve another person in the earlier shift, while in a general shift, it's only the work that's involved. Hope you get the point.
Understanding HR and Numbers
Regarding your remark 'I think HR also involves numbers,' I am not sure what you mean by this—doesn't sales/marketing also involve numbers in terms of targets and forecasts? Had it been a move into finance or accounts, you may have a point.
Looking at these queries from another angle, maybe this could be an opportunity for you to work on your limitations? Give it a thought.
Please note that this is not to justify or sell the idea of moving to HR—just the various and different angles from where you would need to look before making a decision.
Impact of HR Decisions
There's one point that you didn't mention—not sure if it was considered by you: in general, decisions by HR have, relatively, more far-reaching effects than sales/marketing—at your level, which leads to the aspect—How good or bad are you in thinking a few steps ahead before you take any decision now? If your nature is to focus on the now and this, then HR may not be the right choice for you—not that this attitude can't be developed, but it takes time and depends on, like I mentioned earlier, how deep your interest in HR is. Like the saying goes: Where there's a will, there's a way.
All the best.
Regards, TS