I hate this sort of thing due to my experiences with depression:

Visualizing your dreams and maintaining positive thinking can really help a suffering individual, but all you hear about is this "The Wish" sort of zealotry and you think "Obviously I cannot achieve literally anything and everything in life" which makes it all feel hopeless - like the only kind of people who benefit from positive thinking are those who already don't have any problems.

For people like me it takes massive amounts of CBT plus lowering my expectations and dreams to things that are realistic in my situation (which sounds awful but has made my life much better), and it causes a lot of dissonance when people act like it should be as easy for me as it is for them.

I don't know what your relationship with your dad is like, but if I was in your shoes and comfortable doing so, I would consider telling him that you appreciate his good intentions and that you will do your best to keep your head up and make your dreams come true, but that there will be failures and setbacks in life and it is not helpful not productive to pretend that anything is possible. That puts the onus for any and all failures entirely on your shoulders which is extremely unfair as well as a self-destructive perspective. And moreover it's not the way the world works - or else some of those would-be world rulers would have actually been successful by this point in time.