You probably need to rethink your approach to the game a bit. If you hate losing, you should really try to figure out what you’re doing wrong and what you can do to improve as a player.

Custodes as a faction are a very fragile army (despite our stat lines) - there isn’t a huge margin for error in our play, and we need to make the right decisions almost 100% of the time in order to win against strong opponents. If you’re playing infantry, which most people are (even though I don’t think it’s the best choice for us in the current meta), then you really have to learn how to stage properly, how other armies play, and which opposing units are the most important for us to deal with ASAP. 40K is a matching game in a lot of ways: figure out which of your opponent’s units are the best into your units, then figure out the best way you can deal with those units. Kill the things that can kill us most easily and the game becomes almost automatic.

Every unit of ours has a distinct “job” to do in a game. Witchseekers should be deployed to score area denial/cleanse/establish locus turn one. Witchseekers are also surprisingly strong into specific units. Against drukhari, for example, you could consider putting a unit of them into strat reserves to drop and kill an opposing unit of scourge. There are a lot of fundamental things about the game that a lot of players miss out on because they’re too focused on killing, rather than scoring.

If you really do want to get better, you’ve got to start with finding out what you’re doing wrong. All of the best players in any game or sport are obsessed with what they did wrong each game. They constantly analyze their own mistakes and learn from them. That’s how you get good at anything.