Abandoning a course of study for personal reasons, whether temporarily or permanently, is not by itself a bar to future entry.
(Of course, there is a small chance that the law could change, but the probability of such a change is so small as to be effectively zero.)
One can imagine all sorts of reasons related to mental health that might cause you to abandon your studies and also pose a problem for reentry. A thorough lawyer might qualify advice with reference to these possibilities, to ensure that you understand the situation fully. For example, someone who committed a violent crime would be inadmissible to Canada. But the fact that lawyers have to mention these things doesn't mean that they're necessarily going to be problems for you. You are in the best position to know that.
Another thing that could affect you would be the impact that your story has on a border officer or visa officer evaluating your future application for entry. Such a person might be led to a heightened suspicion that you meet some criterion of inadmissibility. But, assuming you don't in fact meet any of those criteria, this would only mean that they look at you a little more closely, find that everything is okay, and admit you or grant your visa.
As a personal anecdote, somewhat related, that should help put your mind at ease, I can offer the story of someone I know who was approved to immigrate to Canada and then, after receiving all of her documents, decided not to go there so she could accept a position with the United Nations. She now lives in New York, and has several friends in Canada whom she visits frequently. Until a few years ago, she had to get a visa to travel to Canada, and at her visa interviews, she was always asked about why she abandoned her chance to immigrate. After she explained, the visa officer always granted her visa, and she has never had trouble entering the country.
The decision to withdraw from a course of study is difficult and stressful. You should not add to that by worrying about the effect it will have on your future ability to travel to Canada. Do be certain to coordinate with the foreign student office at your institution. Ask whether you need to inform the Canadian immigration authorities. If they don't know, ask the immigration authorities directly. It's likely that such a step is unnecessary, but you will sleep that much more easily if you know for sure.