Somebody else already recommended you Richard William's Animator's survival kit. I suggest you to look for the chapter about straight ahead, pose to pose, and the third method which is a combination of both. That, and onion skin, will be your friends for keeping proportions.

"AlanBeckerTutorials" Youtube channel has a video about the twelve principles of animation. The part about pose to pose and straight ahead will give you more insight about that.

Something else that will help you as an animator. Act what you want to animate,imagine the action well or search for a reference and measure the time. Of course, as an animator time is something you can play, so you can increase or decrease the timing when interpreting the action as you desire. Imagine yourself as a sort of actor.

Blinks can be both fast or slow. Just be sure which you want.

a tip i can give you is keep the head always at the same size it needs to be static. your head doesn't shrink when you close your eyes. and when you have a head that doesn't move on every frame then you can edit the eye to close themselves. best way to see those kind of small detail is by looking at yourself in a mirror then restranscripting those movement on paper since this is a eye closing video you should video yourself and then watch every frame and how your face moves. i say you have a much potential as anyone else to be a great artist and don't stop trying. i'm sorry i can't give you 5 stars bc the animation is pretty meh but i will give you 3 so don't stop trying so that i can rate your next animation with a 5 :D

Onion Skins are your friend! Use onion skins in your animation software so you can change what needs to be changed the way it needs to be changed, at the rate they need to be changed, and to double check what needs to stay the same.

I commend you for hitting the ground running by tackling frame-by-frame animation. That's the way to go, and it's a style of animation that, if you can master it, that skill will translate across any software of the era. The software may change, but the fundamentals of animation that come from mastering frame-by-frame movement will not- you can only improve by learning new techniques. Smears, exaggerations, etc...

I bring this up because the OC's hair here, in the animation, is hella wobbly. To the degree that the shape of the OC's head completely changes once they go into full blink. Ask yourself critically, is it necessary for a character's hair to move this much just to blink? If you were going for dynamic hair movement, like it was caught in the wind or something, what could be different to better sell that effect to the audience watching this?

You're off to a great start! I highly recommend researching more about the process of animation if you want to get better at this. Be curious, be proactive, and hungry- seek & destroy, search for the knowledge you're missing that'll help you become stronger at this.

An excellent place to start was a book that helped me out through college, Richard William's "Animator's Survival Kit."

You can find a free .pdf of it if you google it, and that's a pill of knowledge that'll surely help you grow as an animator if you're serious about this.

I wish you luck! Keep practicing, and challenge yourself so you grow!

Good start. Theres lots to learn so what ever you do dont beat yourself up. One quick tip is to animate in layers, copy and past the things that dont move and animate on top of them. And just keep going, the more you do the more you learn.