Without parents' guidance at the initial start of our lives, life would've been difficult for us.
[Do not use written contractions unless you are quoting dialogue.
Here, use WOULD HAVE.]
You can remove INITIAL because the start is "initial".
"Without parent's guidance at the start of our lives, life would have been difficult for us."
You could also express the idea this way, which is how I would word it.
"Parental guidance at the start of our lives, prevents many difficulties later in life."