Anything is OK in moderation. Some people can moderate themselves, some people can't.
People with screwed up lives should not be smoking marijuana. People with problems at home, problems in relationships, problems at work, problems FINDING work, people with other addictions, etc, should not smoke.
Its not that marijuana insta-demotivates you. It might if you let it, but it never has happened to me.
It CAN be used as a crutch however. People can use it as an excuse for their own ****ups, which is why it gets such a nasty name. Anyone can say "Oh, I don't have a job at 40 because I smoke pot." Truth is, you don't have a job at 40 because you are a pace of shit that smokes pot all day.
If your life is messed up...set down the bong and straighten yourself out.
Yeah, its a healing herb and makes everything better IMO...but you can't use it to find answers to your screwups.