Getting rid of stuff can be a highly emotional, highly charged experience. It's not necessarily something you want or will be able to do on a whim. That being said, if you're ready to sort and purge, I say go for it!
There's no right or wrong way to downsize. The important thing is to get started when you feel ready and have the energy to do so. Just remember to take it one step at a time. Once you start going through stuff, you'll build momentum and might even find that you feel lighter. If you start to feel overwhelmed, that's a good sign it's time for you to take a break and come back to it later.
Most importantly, remember to give yourself kudos for getting rid of stuff you don't need anymore. You're creating space for what really matters to you, and that's an awesome thing.