I don't feel it has cost me anything. Not any relationships, not any jobs, nothing really. I used to go after work and kick it at the bar everyday. I used to drink everyday and play pool. It was fun, but it cost me relationships, nearly my job and lots and lots of $$$$$$..
I don't think that weed makes motivated people unmotivated. I think it makes unmotivated people more content, but that ain't the same thing.
If you wake up in the morning before work and smoke a bowl, it's probably hurting you more than it's helping. If you get home from a long day of work and like to smoke a bowl, it may very well be helping. It's up to each individual to evaluate their own actions and habits and to make the determination if something is better or worse for them.
I definitely know guys that need to stop smoking, but they were lazy piles of shit before they started smoking bud. They weren't destined for greatness from the start and have only used weed as a method of self-handicapping.