One thing I can highly recommend is, take your time and use the testnet. Thinking mainly of BTC here, but I believe all major chains have testnets, and I think all prominent cold wallets support them.
The problem with self custody is you are the biggest risk, and it's easy for one to misjudge one's own capabilities over time. Misplace this, forget that, misunderstand this, etc.
A testnet allows one to become familiar with all of BTC's features, with zero financial risk. You can test transactions between wallets, test destroying wallets and restoring from backups, test things like coin control and replace-by-fee transactions. Test restoring a cold wallet to a hot wallet, test running your own node, etc. And most of all, test your own memory - create some wallets, do some transactions, use passphrases for separating wallets, completely forget about all of it and come back 6 months later to see if you can still get your testnet coins back. If you fail at anything, you know what to work hard on or avoid when using real coins.
