Death

When you die, you respawn elsewhere, and are unlikely to find your old base again. It is unwise to go looking for it, especially on the first night.

If you are lucky, you may encounter a broken heart. These are incredibly precious; you can craft each one into a heart that will temporarily increase your maximum health. Each death will increase the chance that you lose one of these hearts, so treat each life with care. [For more info, search "broken heart" in JEI and view the tooltips]

A backpack with an eternity upgrade can be a practical safety net in case of an unexpected death, but the upgrade will vanish after you die. With nesting upgrades, ender chests, and alchemical bags, there is no shortage of storage you can create that transcends time and space, provided you can afford it. If you are lucky, enchanting a tool or spellbook will apply the soulbound enchantment, which will cause the item to stay in your inventory after death.

Death has a variable effect on your ability to recall magic. Some knowledge is preserved. Some knowledge becomes suppressed, and you may have to go through some beginner's steps before the knowledge returns to you. Some knowledge is simply forgotten. As a general rule, rote arcane knowledge tends to be preserved, whereas knowledge that perturbs the mind or body is more likely to be suppressed or lost. This can be a setback, but it also allows for a fresh start.

By the way, if you haven't crafted a shovel yet, you really should...