It is a very real phenomena and can be dangerous. As already mentioned JFK jr is a prime example of what can happen even if the circumstances were slightly different, the end result is the same.
Spatial disorientation is a very odd sensation and a hard one to rail against unless you are prepared. It is very unsettling and you must force yourself to believe your instruments. Not easy when the senses you rely on every day are screaming at you that something is wrong.
Practice and being forearmed are the only ways to try and combat this problem.
Whilst it happens less frequently to me now, I do occasionally get the "leans" and that's despite having a fair few hundred hours in actual IMC. (Not just under IFR).
Get a bit of time under the hood and make sure when you are flying in these conditions that you get the a/c well trimmed out and don't over control. try and keep something for reference and remember haze is always worse when flying into sun, if it all gets too much, look in another direction, you may have a better chance of finding something resembling a horizon, just be aware of false horizons, they really can be disorientating.