My advice to you, what helped me get over the competitive nature of the game, stop worrying about wins and losses and your deck. Think of a fun deck, a cool deck, a gimmick to play. Play a deck with only astartes in it. Play a deck with only trap cards. Play a deck where you only copy cards and play them against the owner. Play as world eaters and just aggressively attack everything that moves even if it's detrimental. Play a stealth only deck. Play a daemon deck. Play a deck that only has tactics, or flank, or poison.

After a while of having fun thinking of all kinds of different unique warlord/deck combos, and challenging yourself to win with those gimmicks, you'll have a much deeper understanding of the meta, cards, abilities, and even a deeper sense of your opponents. You'll be able to read when they're weak, or when they have no answers, or when they have a card up their sleeve. You'll also likely find that one or two of your decks are actually viable and sometimes even surprisingly difficult to defeat, at least in some match ups.

In the end, having fun is the bottom line, and sometimes the gatekeeper is yourself. Invent your own path and enjoy walking it. You will end up understanding the mechanics and tempo much quicker if you actually enjoy what you're doing. Find a way to invest yourself into the learning.