After Harry Nilsson, for me, the obvious artist to go to is John Lennon.  Being a massive fan of The Beatles and Lennon is the reason that I even know who Nilsson is.  During 1974, in what is known as Lennon's "Lost Weekend" he rekindled a friendship with Nilsson and also went a little off the rails.  During the 18 month "Lost Weekend", Lennon caused a fair amount of trouble, along with Nilsson, and got a lot of bad press but he also was musically productive and collaborated with several musicians, including Elton John, David Bowie and Nilsson.  Lennon produced Nilsson's album Pussycats and on that album they recorded a song together, by Jimmy Cliff, called "Many Rivers To Cross".  It's a great song, one that is uplifting when you are feeling a little lost despite the fact that the lyrics aren't exactly cheery.  Considering all of the songs I could choose from for Lennon this is not an obvious choice, which is partly why I decided to share it, but don't worry I'm sure I'll be mentioning Lennon regularly and sharing more of his work because I love him so!  So take a listen to "Many Rivers To Cross" it might keep you company when you are feeling a little lost or lonely... it certainly does me.