The psychedelic experience is not something that should be undertaken lightly. While you will be physically OK after the trip, and odds are you'll still have all the bolts in your head screwed in right afterward, the trip is very likely to cause lasting mental changes. All the following effects are strongest in the days or weeks after the trip, but they may well continue in some form for the rest of your life. You may see mild hallucinations in dark rooms or with your eyes closed. Objects may seem to vibrate. After prolonged use tracers and open-eye hallucinations may appear. Especially immediately after the trip, you may experience odd mood swings and irrational impulses (harmless ones, but people may still think you're nuts if you fulfill the impulse of "Gee, I really want to jump up on that rock and bounce on it because life is so wonderful"). Your perception of objects is very likely indeed to change. You may become captivated by sights such as snow falling on a dark winter night or the shadows caused by
a candle flame.
Insights acquired during the trip may also have lasting effects. There are many cases of people discovering a hidden aspect of themselves, ie. that they are homosexual or that the philosophy/religion they have adhered to their life is wrong. While the insight itself may be beneficial, the process of adjusting to it is often painful.
Very few LSD users regret taking the drug, but before taking it one should still be aware of what may happen. LSD is not an ticket to nirvana or the cure to all the problems of humanity.