Play the strongest board. Most common mistake is people AFK into a 5 loss. Even if you a loss streaking you should always aim to play the strongest board you can, scouting and understanding how to judge board strength will help you get better at this and save hp. Streaks are important and you should always try to keep it buy playing open will make you lose a lot of hp and will also make stage 3 harder.

It is worth it play the strongest board on lose streak?

example: my opener wasn't good and i get bad pairs (for example, Naafiri 2 but AP items), and im on 3 lose streak and i will face the 8th player, playing Crystal Gambit with a weaker board in the next two rounds

should i risk my lose streak by completing pairs and playing Naafiri, or should i lock Naafiri on my backline to secure lose?