Certain vitamins your body will dispose of safely (like vitamin C), but there's others that just build up until they kill you; there's the case of Xavier Mertz [0] who was theorized to have died from an excess of vitamin A after eating his sled dogs' livers.
But the basic rule is: just eat normally / "a balanced diet"; you likely don't need supplements unless you have absorption issues or stick to a specific diet (e.g. vegetarianism / veganism, soylent / diet shakes, or the same thing every day, like the 14 year old who only ate chips and ended up (partially) blind due to a vitamin deficiency [1])
[0] https://en.wikipedia.org/wiki/Xavier_Mertz
[1] https://www.acpjournals.org/doi/10.7326/L19-0361, https://www.cbsnews.com/news/british-teenager-went-blind-fro...