I remember being relieved that the mud wasn't as sticky as in 1997, because it there was much, much more water.
I was ill in 1998, not from overindulgence - a cold or flu. So I spent most of my time in my tent, eating weed. I became convinced that all the bits of mud on my tent were actually slugs and I sat/lay in the darkness for what seemed like an eternity. As a teenager on his second festival, I didn't have things like a torch or a hi-tech Nokia to illuminate matters. I told myself they weren't slugs, they were just balls of mud and to pull myself together. With a great deal of effort and a trembling hand, I reached out and grabbed one of the "slugs"... PHEW! It was mud, hooray! Then I looked around at all the other splats around my tent and had the awful thought "I know that one isn't a slug - but what about all the others???? "
Sadly, I was still a newcomer and hadn't quite got past the idea that sticking in front of the Pyramid wasn't actually the best way of ensuring value for money, so all my headliners were at the main stage.
Primal Scream (from my tent in the rain)
Blur - they were brilliant, the eponymous album came across really well echoing over the Pyramid arena.
Pulp - a great set, but didn't quite live up to the expectations of their legendary sub bump-up from 1995 - watching them was one of the things that made be determined to finally attend Glastonbury the next year.
Bob Dylan for a bit, until I realised that he had been playing songs I technically knew, but they were totally unrecognisable and not for the better. I wandered off to see Bernard Butler without any regrets - one of the liberating things about Glastonbury is that there's so much on, even the most revered musical figures have to earn it. To paraphrase a contemporaneous hit "So you're Bob Dylan? That's don't impress me". Possibly one of the moments I truly got the Glastonbury bug.
James Taylor Quarter - randomly wandering around with @fatyeti24, sharing goodies, having no idea where we were, or who was on the stage until he said "aren't those the band that don't have any words."? At which point I realised I was at a stage called "Jazzworld"