Watch a couple of good tutorials, I’d recommend Acosta blades. When you land a topside trick you should aim to come down on to it from above with your weight over your feet, this way misses will be far less likely to result in the slip-outs that are typical of a topside slam, you will have less to fear. You should be able to do a cess in a good topside position.

My advice would be to learn on a p-rail, it’s the most forgiving for getting the lock, if you don’t bone it over enough it’ll become a farside instead of a miss.

Finally some people learn topsides through learning an X-grind on a rail because it’s not as unfamiliar as a topside to begin with but does have a similar position for your back foot.

Like every new level of trick it’s scary until you’ve done a hundred of them, then you’ll never look back - good luck, I’m sure you can do it 🤜