Any mental activity is easy ...

Any mental activity is easy if it need not be subjected to reality.
Any mental activity is easy if it need not be subjected to reality.

More phrases

Don't settle in the land of barely enough. That is where you are, it is not who you are. That's your location, it's not your identity. No matter what it looks like, have an abundant mentality.
The by-product is that they more people you help, the "richer" you become, mentally, emotionally, spiritually, and definitely financially.
 T. Harv Eker
Happiness doesn't depend on any external conditions, it is governed by our mental attitude.
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is.
To improve is to change; to be perfect is to change often.

Quotes from the same author

We don't receive wisdom; we must discover it for ourselves after a journey that no one can take for us or spare us.
Let us be grateful to people who make us happy; they are the charming gardeners who make our souls blossom.
The truth is that men can have several sorts of pleasure. The true pleasure is the one for which they abandon the other.
For everyone who, having no artistic sense-that is to say, no submission to subjective reality-may have the knack of reasoning about art till doomsday, especially if he be, in addition, a diplomat or financier in contact with the 'realities' of the present day, is only too ready to believe literature is an intellectual game which is destined to gradually be abandoned as time goes on.
We are able to find everything in our memory, which is like a dispensary or chemical laboratory in which chance steers our hand sometimes to a soothing drug and sometimes to a dangerous poison.