for the days when you're not quite feeling it:
if nothing grabs hold of you when you sit down to create, don't force it - quality is better than quantity. lighten up.
the value of play is often underestimated - it's not only a great way to have fun, but it's good for your health and stress levels, and exercises your brain in terms of flexibility. remember when creating something first took hold of you? you'd take some time and genuinely just dabble in your craft. you'd try various techniques and approaches and eventually, you found a way that you thought worked best for you.
keeping this in mind, on the days when you're not quite feeling it, try switching it up.
(penicillin was discovered purely by accident - you too could come across a new favourite colour combination, inspiration or technique purely by changing your routine.)
are you a painter who plans? plan less. just put paint to canvas and see where it takes you. mixed media? put together two textures you haven't worked with before, and that you're not sure will work. writer? just write. don't edit.
too often we censor ourselves in the interests of time, expediency, fear, or convenience. remember: fortune favours the bold. take time for a creative stream of consciousness, uncensored and unhindered by expectations.
and hey - if it doesn't fly. it's ok. you were just playing around anyways.
for the days when you have so many ideas of things you want to do, but you just can't seem to find the time nor energy but you feel like you're going to explode out of your skin:
breathe. deeply. you'll get there. rome wasn't built in a day. the sistene chapel wasn't painted in a week. turn your music down and lower your shoulders for a moment. or dance crazily to your favourite song. lean back in your chair, close your eyes. or go for a run. something. anything. whatever floats your boat. just don't stress yourself out too much, because there's only so many hours in a day. worrying about it won't extend it.
i know that it's easier said than done, so i find it helps to be a little proactive. keep a little memo pad to jot down your ideas as they come to you. don't focus on getting it to look pretty or about developing each idea fully - the key is to just get them down. once they're committed in ink, consider them to be out of your mind. they're safe on paper. you won't forget them. so write them down, and continue on with your day.
when you're feeling more settled, take a minute to flesh them out a bit more. some will work out; some won't. try not to worry so much about those ones. it's normal - but more importantly - it doesn't mean that you've failed. no no - not in the least.
(if anything, it could be considered a sign of wisdom to know when to continue with a project and when it's better to stop spinning your wheels.)
in a time when people are sucked (or sometimes dragged kicking and screaming) into a 24/7 more-better-faster lifestyle, it's so important not to burn yourself out. there's a time to work, a time to play, and a time to give your brain a rest. you're an incredibly talented + busy person - remember that even the most productive people in this world need to take a moment or thirty to themselves to rejuvenate. your output will thank you.
so save all of those brilliant and unruly ideas for a time when you can truly+ fully immerse yourself in them. you'll come out with a better quality product - and (quite possibly more importantly) you'll be able to appreciate the process more.
in the meanwhile, if you're stuck in the middle of that kind of day... your first step is to just breathe.