I've had several experiences that I would label 'mystical' or 'otherworldly'. Those experiences changed me and continue to do so. I, also, learn a great deal from others that have had similar experiences. For example, the following from neurosurgeon Eben Alexander:
Those memories began in a primitive, coarse, unresponsive realm (the “Earthworm’s Eye View” or EEV) from which I was rescued by a slowly spinning clear white light associated with a musical melody, that served as a portal up into rich and ultrareal realms. The Gateway Valley was filled with many earth-like and spiritual features: vibrant and dynamic plant life, with flowers and buds blossoming richly and no signs of death or decay, waterfalls into sparkling crystal pools, thousands of beings dancing below with great joy and festivity, all fueled by swooping golden orbs in the sky above, angelic choirs emanating chants and anthems that thundered through my awareness, and a lovely girl on a butterfly wing who proved months later to be central to my understanding of the reality of the experience (as reported in detail towards the end of my book Proof of Heaven). The chants and hymns thundering down from those angelic choirs provided yet another portal to higher realms, eventually ushering my awareness into the Core, an unending inky blackness filled to overflowing with the infinite healing power of the all-loving deity at the source, whom many might label as God (or Allah, Vishnu, Jehovah, Yahweh – the names get in the way, and the conflicting details of orthodox religions obscure the reality of such an infinitely loving and creative source).