Email is awesome but not if it is managing you instead of you managing it. I get a colossal amount of email a day, but I keep it under control, so here's a few tips that can help you manage your inbox, AND make it so you can find those emails you need when you need them.
Number 1. DELETE NOTHING (unless it's abusive). There is plenty of space in your GMail inbox, so chillax, let that email slumber sweetly within your nice and comfy inbox. It's OK.
Number 2. Read them all, it only takes a click, just open one at the start (or end), and keep clicking through until you get to the end (or the beginning). You might find this easier to do on your phone than in your browser...
Number 3: STAR (or Flag) emails you have read, but need to follow up on, then unstar (Is that a word? It is now) them when you're finished. Just click on the star icon.
Number 4: Use the Starred option in the menu to easily view just the Emails you need to deal with.
Number 5: Create a label (folder) to drag and drop email that you want to be able to easily find later.
Number 6: Use the Search option, your very own Google search, but focused on your Email.
Number 7: In GMail you can even use more than one star, just keep clicking the star, you can choose which ones you find most useful - urgent, information and so on.
Number 8: CHEAT. Look you are never going to read those 4276 emails (yes I have seen that many) so let's just start again, and keep a clean slate from now on OK? Here's how to mark all of those emails as read.
Number 9: Use another 'client' to make staying on top of your mail easier, eg the Mail app on your Phone, iPad, or Mail on your MAc, all of these make skimming through your inbox easy (I use the arrow keys to move through them quickly), and all of these allow you to flag an email for follow up - just choose Mark - Flag and it will sync with our GMail inbox.
Number 10. Um. There is no more, so why not use this time to READ YOUR Email!