To be successful in their job, by necessity, VCs are friendly and personable. So friendly that it is easy to be lulled into thinking you are forging a real friendship and that they can step outside their fiduciary selves and provide good unbiased advice to a startup founder who needs good unbiased advice a lot. But it is vital the startup founder keep in mind that the VC has a job to do and they are driven first and foremost by that job even in the advice they provide.
There are two experiences I have had that illuminate this. One was when asking a VC for professional career advice, and the other was when an investment I was CEO of no longer looked like an investment worth continuing. They intersected at the same company with the same investor.
I was a successful multi-time CTO who sought to build skills toward being CEO of an upcoming startup. To do that I needed to get sales and marketing experience as well as specific CEO skills such as raising money.