I completely agree with you on Halcyon and On and On... in fact many songs from Orbital have that "emotional" aspect that leaves you reflecting on your life when you finish.
With that being said, I'm here to contribute some songs to the thread:
https://open.spotify.com/track/2CH4mc6qWAI3ejAdqpON9B?si=c2aabf5388a5407e
Orbital's "Belfast" is near the end of their 1st self-titled and I have always found this song to be so captivating after the duo basically destroys you with the big beat style of the 90s...
https://open.spotify.com/track/5RQjC6zC0Jj166iNydg654?si=b244758c6f894469
Squarepusher's "Tommib Help Buss" is a quick song off of Ultravisitor, a much more personal and down to earth album from Tom that makes me feel happy to be alive and grateful for the people and things around me... Definitely gives me christmas vibes whenever I play it
https://open.spotify.com/track/21Phj46KeUHOWyZW9A9b7P?si=1b4de617263949d7
Possibly Aphex Twin's most notable song to date outside of Avril 14th and On, Alberto Balsalm gives me empty shopping mall vibes and additionally gives me the reminder that everything will be okay and to always keep pushing forward despite whatever adversity that you have. Similar things can be said about #3 (as mentioned by Meapers)
https://open.spotify.com/track/1aaIYTqoRDzRUilU2Q6vTe?si=0f5270a87ae34c2a
Burial's magnum opus "Archangel" is definitely the definite sad track for me in terms of dubstep and reminds me to of course, never be alone and that there is light at the end of the tunnel.
https://open.spotify.com/track/56p0LzMVbPMQU4Gf5rsK8e?si=bc91bf08a0604508
Autechre's "Garbage" EP is definitely one of their greatest releases to date and often goes unnoticed outside of the duo's unbelievable albums later in their career. "VLetrmx" is the last song on this EP and for a group notable for leaving emotion out of their music, it leaves me to reflect on my life and all the struggles that I've gone through along with where I've ended up now.