How to determine if a decline is too steep for safety?
Ultimately there is no limit to what you can ride beyond your own skill. Many people say "too steep" is a cliff, but some riders just look at that like a drop and ride it anyway.

You need to evaluate whether the places you are walking are because you lack the skill to ride them, the confidence to ride them, or improper equipment. Yes, you could theoretically ride an entire downhill track on a fully rigid, carbon XC bike, but wouldn't it be a lot easier on a 8" travel, full-suspension bike?

Looking at the steep section that flipped you over, see if you can find why you flipped. Too far forward on the bike? A big rock/root in the way? Application of too much front brake? Remedy each of these things and you might find yourself riding steeper and steeper hills.

So how do you fix it or get better?


Practice! Hours in the saddle is the best way to get more confidence riding these types of things. Find a smaller decline and practice shifting your weight back, feathering your brakes, and keeping your eyes scanning for obstacles.
Ride with someone Don't underestimate the value of riding with someone better than you. Politely ask them if they could show you how to ride some of things you're struggling with and watch them do it and have them watch you.
Speed is your friend I know it seems counter intuitive but like riding over rocks/roots on flat terrain, a little speed goes a long way. Again, practice this, don't just go charging over the edge of a super sketchy hill and hope for the best (although that can be really fun).


Lastly, what type of riding do you want to do? A lot of XC trails are relatively tame in regards to steep downhills because the bikes aren't really meant for that. But if you're looking to get into freeriding or downhill you'll need to get comfortable with this.