The single guiding thing in parenting for me is, was, and always will be: Absolute love, absolute boundaries. The framework that gifts both you and your child/ren is priceless (and also often offers the solution when you're sitting there thinking 'Oh my God, how do I handle this?' 
The second - and I am in zero doubt that others will have said this too - is This too shall pass. One thing that did take a little time for me to realise though was, that whilst I had thought of that often in the middle of any 'tough' stuff, it also applies to the great stuff - it will pass so cherish it whilst it's there.
Having now parented babies, toddlers, young kids, older kids, teens, and now young adults too, with utter certainty I can state that this is my experience of a simple framework of what children really need and want from you:
For you to be 'present' - don't be just vaguely listening to them as you do some task or other, hear* them and respond; a child who is heard is a child who will know he/she is of worth, is likely to develop a strong sense of self-esteem that will carry them long after your arms are able to do so.
To have their basic needs always met: to be fed; to be kept clean; to equip them* with the skills to be able to feed themselves/keep their own clothes and bedding clean once they are old enough to do so; to guard their emotional health as much as you do their physical health, and to teach them to know how to do the same; to be made to feel safe; to know they can always talk to you (no matter how 'bad' they might feel what they have to tell you is!); to have the security of a routine but whilst avoiding that routine being so rigid it gets in the way of actual life and steals little moments of joy.
- To then in turn pass on what you know to them, to always - no matter how 'old' they may get! - ensure they know they have a backstop; that when in need you are there for them at 21 just as much as you were for them when they were 1. Their needs may change, as will the way you meet those needs, but their need for you to always be there for them is a constant IME.
And again, absolute love and absolute boundaries - even when the proverbial has hit the fan, offering my children both of those has never yet failed us!
Just writing the above has actually made me slightly melancholy about the pre-school years that have long since passed, so my advice to anyone reading who still has toddlers is to absolutely not sweat the small stuff and focus instead on enjoying those beautiful moments; they will pass sooner than you think and I promise you will never look back and say 'I'm sooooo glad my sock drawers were always tidy' 
- but you might look back wishing you had cut yourself a bit more slack to instead enjoy the moment a bit more...