In the blockchain technology, we are responsible for our own security and hence we have to take maximum measures to ensure that our assets are secure at all times.
Your wallet, which serves as your digital bank account, is (should be) fully under your control, this means that you have total autonomy over the assets stored on it. There are different types of wallets, but avoid storing your assets on a wallet that offers custodial services; this means the website will control the private keys to the wallet, and, if it's not your private keys, it's not your bitcoins.

So as stated above, it's advisable to own your private keys, but this is a huge responsibility and you have to know how to protect your private keys from other people as we as accidents and loss.
Private keys are an alphanumeric phrase that is used to send bitcoins from one wallet to another. They are randomly generated are linked to every address on the wallet, a wallet can have more than one private key, and hence hold multiple public addresses.

What differentiates a private key from a public key?

A private key is used to authenticate transactions from a wallet address, while a public address is similar to an account number of your bank. It's an alphanumeric key that is used to identify a specific address. Public addresses can change after each transaction, and it's advisable you change them to avoid your transactions being monitored and linked, as they're available to the public. Public addresses are derived from private keys. Private keys are not available to the public and do not change. They can not also be generated from the public addess. They usually start with the number 5 (on the main net and 9 on the test net)
Example of a private key: 5Kb8kLf9zgWQnogidDA76MzPL6TsZZY36hWXMssSzNydYXYB9KF

Private keys are usually not made available to the wallet owner, (although some wallets allow you to import it) rather you are given a seed phrase or recovery phrase. This is a set of words that are randomly generated and are as secure as the private keys. This phrase is used to recover your account should you use your device or wallet.
For example, red yellow green blue black brown purple grey orange indigo violet pink white

How best do you safeguard your recovery phrase?

Your private keys or seed phrase are too long to be memorized comfortably and you should never screenshot or keep a copy of it on your device. This exposes it to hackers and malware. When securing a recovery phrase, you have to consider online threats (hacks and malware), unforeseen circumstances/accidents; such as fire or water disasters, and keeping it away from other people. Simply writing it down in a piece of paper does not provide the needed level of security especially when you have a high amount of bitcoins.
There are a few ways you can securely back up your private keys and recovery phrases;

Use a hard drive: you can store your private keys or recovery phrase in a hard drive, which should preferably be permanently offline. This way it is not exposed to online attacks and can be easily recovered. You can also secure the drive with a password and store it in a vault to protect it from others.

Paper wallet: a paper wallet is primarily designed to store private keys. The details (which may include QR code are imprinted on a price of paper). This can then be laminated and stored in a vault.

Using a steel wallet: Your private keys can be engraved and stored in a steel wallet, such as cryptosteel. Designers of these products claim it is resistant to hazards such as fire, water, corrosion, etc. This would make it an effective way to store your private keys and/or recovery phrase

Note that when using any of these measures, you should always have multiple copies securely stored.
How do you safeguard your private keys and seed phrases? Also, how would you ensure the bequeathing of your assets to your next of kin(s), besides adding it to your will?