Never assume that you know someone else's motive for doing something. If understanding their motive is important to what you're trying to accomplish, find out for sure. And usually the best way to find out is to ask.
For example, let's say you've identified a piece of property you're interested in buying. Knowing the seller's motivation will help you put together an offer that will work for everyone. But even though you may see signs that point to a particular motive, verify that you're on target. The property may be in disrepair and look like a headache that the owner just wants to be rid of -- but it could be that the real motive for selling is to get cash to pay medical bills. In the former situation, the seller is more likely to accept a no-money-down deal and hold all or some of the financing; in the latter situation, the seller will likely insist on at least some cash.
Most real estate sellers will be honest about their reasons for selling and what they want out of the deal. To find out, all you have to do is ask.