For me the most regretful decision would be for selling my coins at $1400. I didn't sell everything the only thing i regret was i didn't utilise those money which i sold and later i realised if i didn't sell it i could have got more profit from holding bitcoin rather than investing it.
Yeah that is a bummer. I have come to learn that I have regretted selling any coin at any time since the start of cryptocurrencies. I have made some profitable day trades when the conversion or pairing ratios have been good between BTC/LTC or BTC/ETH, but on the whole, I would have definitely done better in the long haul just holding onto every single coin of every single type that I have ever purchase or received from the sale of a good.
That is why I am a big proponent of just holding everything you can and be as diversified as you can (in case one coin kicks the bucket), unless you absolutely need the money at the time to support yourself of your family. Selling coins so that you can purchase some sort of gadget, toy, gambling...anything like that will almost certainly leave you regretting it. Maybe you timed it just right for today...like if you sold at $3500+ and the price is now in the $3300s...but years from now, you will more than likely wish you hadn't sold.