Secure passwords don't have to be hard to remember.  In fact they can be a lot easier to remember than a weak password.  People have been told to replace letters with numbers and capitalise things, it's what we consider to be a strong password.  The problem is, that attackers are also people, so they build systems to exactly that.  So for example the password "dragon" (which believe it or not, is one of the top 10 most common passwords of 2017) is just as strong as the password Dr4g0n.  Both of these would be cracked within a 100th of a second by a popular easy to get-hold-of password cracker.  So it's all about doing something different, but importantly something different and future proof that attackers will find hard to build a cracker for.

The answer is randomness.  Currently we think of passwords in terms of collections of letters and numbers. Let's call each individual character a "bit".  So the randomness of each bit of the password is going to be one of 26 letters and uppercase letters and a handful of numbers and symbols, it's quite a small set in reality.  To make it stronger we need to increase the randomness of each bit.  We do that by considering a password to be made up of a collection of words, rather than characters.  Instantly you then increase the randomness massively - there are a lot more words than there are letters.

The great thing is that, this also makes it so much easier to remember. Rather than remembering where you replaced letters for numbers, or where you capitalised, you have to remember a series of words.  You can create a little story in your head and make that the password.  For example, on my desk I have a bottle of elderflower cordial, a soup spoon, a calculator and a pencil.  So my password could be elderflowerSpoonCalculatorPencil - that in itself is a damned good password, and not too hard to remember at all.

For more detail about all of this, if you are interested have a look here which will take you to an article written by dropbox all about how they handle password security.  Their password security checker - zxcvbn - or variations of it has been adopted all over the place, including within MINTclass.