How do you know that you actually figured out the meaning though?
How many words did you guess wrong about and now you think you know but you don’t actually. You’ll never know if you read the context properly without looking it up after.
Try to guess the meaning of the word lugubrious from the following sentence:
Although he was wealthy, he often found himself lugubrious.
There isn’t a single clue in that sentence as to the meaning of the word.
Don’t just guess; actually learn properly instead.