There is nothing quite like flight.
Rainbow Dash has tried to explain it before. I figured it was just from her inability to string the right words together. That there must be some way of describing it to a pony without wings. But it truly is noting that can be described using Equestrian words.
The mixture of feelings is far too complex. The sensations, the thoughts, the views. Individually yes, they can be described, like the feeling of momentum trying to keep my trajectory strait, or the feel of the wind flowing through my mane and across my feathers.
But everything together is something to be experienced, not explained.