Some thoughts at 3500$ for new and old.
Let's say you over-extended yourself and bought 2 BTC at 4k. Consider establishing a stop-loss to limit your liability. You can choose to sell and take the 1000$ loss as a valuable but cheap lesson in speculating; this market is a speculative jungle and you're only making money in the short term by actively playing the market, e.g. if you bought at 3700 and sold at 4400 before price declined again you would be pretty satisfied with yourself.
If you believe bitcoin will eventually become a digital reserve currency or at least see another all time high (ATH) at which you'll sell a portion and want to invest for the long term despite market volatility your other choice is to Dollar Cost Average your crypto. NB: that this does not mean buying in a lump sum, it is profoundly misguided to heavily leverage yourself to "go all in," which is an english phrase used in gambling. If you take this position the wisest course is to budget a small amount you can afford to lose and routinely buy crypto at set intervals regardless of losses.
For example, let's say that you put a small amount once a month into your crypto fund and the price has decreased by 500$/mo. If you bought set amounts at 6k, 5.5k, 5k, 4.5k, 4k, 3.5k then your DCA would be 4.75k/BTC, you're still down but not as badly as if you were to buy once at 6k. Ideally the price will eventually rise, so if you buy down to 3k then at 3.5k, 4k, 4.5k, 5k, 5.5k, 6k, & 6.5k your DCA is still 4.75k/BTC but the price is 6.5k/BTC. Feels pretty good, right? Now take a look at how long it took to get to this point in an improbable perfect scenario: 14 months. Note that this is for demonstration purposes only, not a prediction, and if we actualize sustained growth after this we're probably looking at much longer bumpier road.
If you're new or have pulled out to limit your losses, just be patient and keep watching the price. No one knows how low it will go and trying to anticipate that and exhausting your resources the moment you think we've hit bottom is a recipe for regret. Work on your budget now and when we see a sustained recovery start routinely contributing small amounts to your crypto fund. If you have debt the single most important step you can take towards financial independence is to pay it off and limit your use of credit. Consider building an emergency fund with 3-6 months of expenses before contributing heavily to a risky crypto fund.
Take this exciting/tumultuous period to learn about BTC and how to use it, we contribute to the ecosystem when we participate in further decentralizing the network and the benefits of bitcoin are fully realized when it's used as a currency. Put a wallet on your phone and computer, check out hardware wallets such as the Ledger to store large amounts while keeping spending money on your phone. Offer to accept bitcoin as payment, learn what private keys are and why it's important to hold them yourself rather than letting an exchange hold them. If you just bought some coins on an exchange because everyone is talking about bitcoin but didn't look much further than TAs, you can read this ELI5 article to get you started. Consider reading the Cypherpunk Manifesto and the pseudonymous Satoshi Nakamoto's Whitepaper. Google what you don't understand, ask what you can't find on Google. Andreas Antonopoulos is a bitcoin expert/evangelist/apologetic and has extensive talks/Q&As on his YT Channel.
If you're "in it for the tech" then consider contributing to the Lightning Network by running a node, if you're a tinkerer /u/Stadicus has a pinned post that's a cool crypto project and costs about 125$. Raspiblitz project is linked in the comments to that thread and incorporates an LCD screen which /u/CBDoctor used to make this legit node/art installation. Alternately you can buy a ready-made Casa node for 300$.
Hopefully y'all will post some additional thoughts and suggestions for further reading/tinkering in the comments.