As a guy with multiple deseases (needs more than one hand to count) I'd like to share my experience.
Recently had an interview for a really well paid job. Am still going through the process of being a legal patient which can take anything between 1-3 years. Until then I am bound to stick to the black market sadly.

Since I currently am broke as hell I could not smoke. Was about to get to the company on foot (1 hour walk) without at least having pain and massive panic attacks. It was horrible. I had real problems going there. More problems even at the interview. People notice I act not like others when not medicated. All 420 blazeit jokes aside, it is my medicine. Can live without but it makes life complicated and turns it to hell.

I am not even able to talk openly about it in here because it's highly illegal. So I have to keep it secret when it comes to work.

But anyway I still went there and gave my best. Had weird situations but that's ok for now. I think they want me, 85% chance I get the job.
I got no idea what to do if I get to work there and have to smoke in secret... worries me... But you get it. Where is a will there is a way. And I think I made my way.

If you really do not need mj for medical purposes, do not fucking get high before an interview and keep your god damn shit together. Else you provide others and yourself proof that you are an idiot and do not deserve the job.

If you are allowed to use it for medical purposes and still get your shit together, at least be honest and speak about it. Also provide proof of past projects or whatever that you still are the man when you take your medicine.

Just be a little responsive and think before you do things, like if it's really needed in your case.
Do not feed anti-mj movements by being a stereotypical stoner please.