The old adage "wishful thinking"....believe it or not is directly opposed to spirituality due to the objective nature and reality of it as well as the purpose behind it. It doesn't pander to individual perceptions or opinions because that would work contrary to change and the cultivating process involved.
The process of spirituality is specifically to break up patterns, paradigms, molds, personal perspectives, opinions, wishes, desires, urges ect ect to align with what is objective and actual and worth pursuing. It has a transforming quality to it and therefore that sort of mentality (wishful) is not useful and actually can act as a hinderance. The power behind spirituality drives the participant away from delusions rather than keeping them in it.
Now, this does not mean that the propositions or claims within the spiritual arena will be devoid of mistakes and or absurdities (or even deluded people) of course, because we are dealing with imperfect creatures and their varying levels of expertise or lack thereof. So what you want to distinguish between are aspects of spirituality that are less emotionally involved, and follow the propositions that logically follow and make sense, simplicity and common sense will go a long ways.
The reason I say "less emotional" is because people tend to mix the two together for example...creating laws or commands to kill or cause harm to others that may have different lifestyles and beliefs and claim it was Gods doing. Discrimination, persecution and segregation have permeated the religious square to the point of idiocy and rarely do they play a true role in spiritual development if at all. And you will notice a true spiritual Master will always abide under the umbrella of unity and love or getting souls to unite in spirituality and experience something real rather than pretentious and self limiting.
Since the nature of spirituality and the created worlds are so dynamic they can come across as being "out there" but this is only based on perceptions, there are some incredible (unbelievable) aspects within spirituality but they all fit and work together like a puzzle...nothing out of place unless it is truly out of place or non-existent.
The Creator however is majorly underrated to the extreme, not many people can fathom an eternal Creator and what that really could entail on all levels, and so God is much more dynamic of a Creator than anyone could ever dream.
In a nutshell making the assertion Theistic beliefs, spirituality or propositions are based on wishful thinking is very much in fact wishful thinking. My point being, change your preconceived idea so that you don't end up with faulty premises and false assumptions. To hold this assumption as true would be like walking through life with a blindfold and would only serve to squash the potential of the holder.