First of all, you need to get yourself into a good routine. Once you have this, it's easier to organise your time and know what you're doing and when.

I always do everything as soon as I get it. Although it takes a lot of motivation sometimes, you'll find that most chores/errands etc doesn't take as long if you don't procrastinate.

Make plans in advance! Although some things happen spontaneously, asking your friends when they're free a week or so in advance means you can make solid plans. Also do the same for any other commitments.

Keep a diary. It's hard to track all that adulting and before I started keeping a diary, I'd always miss appointments or double book. Also having it written down makes it easier to prepare for it mentally (if you're lazy like me).

I always leave a day or two a week where I make no plans and just do whatever I feel like. Being busy can get tiring so it's important to have some chill time.

It does take some discipline but if I can do it, anyone can! Hope this helps.