Some offside decision are tight. Some are not. Regardless, if you are not properly aligned with the offside line, you may incorrectly give or not give offside.
In the video below, the attacker was onside by 1.2 meters (about 4 feet). The AR was misaligned by 1.0 meter (about 3 feet). But because the AR was ahead of the offside line, it looks like the attacker was offside. Consequently, the AR raised his flag and the referee called offside. Had the flag stayed down, the attacker would have had a 1v1 situation against the GK.
Remain focused. Use your agility, speed, and anticipation to remain in line with the offside line.