Without Restraint

"This is the law of the Torah; if a man shall die in a tent ..."

This passuk is referring to the chok of impurity - that if there is a source of tumah in a tent ( or any covered enclosure ), the tumah actually envelopes the entire enclosure spreading to it's edges and contaminating anyone who is under that roof.
( This is why it can be problematic for kohanim to enter hospitals, even on floors where there are no deceased patients. )

Chazal, however, interpret this passuk to have another, equally important, meaning. "This is the law of the Torah, it will only be accomplished by one who kills himself for it ... "
While it is clear that chazal are not actually advocating ritual suicide, what are they saying ? That in order for one to really accomplish something in Torah - observance or learning - they must be willing to sacrifice all.
It is only with a no-holds-barred, give-it-all-you've-got attitude that we can truly, properly observe the mitzvos - because only then are we in full recognition of what the mitzvos stand for.
Hashem gave us this life for a goal and purpose - by "putting it all on the line" for the mitzvos we are, in fact, affirming that goal and re declaring that purpose.
If we were to show even the smallest bit of restraint - that we'll give 99% but not a 100% - we are saying that life is ours and we do with it what we please - and now it pleases us to serve G-d. That is not service - that is picking and choosing! In order for us to truly serve we must be willing to go at it without restraint.

( This is, of course, a level to aspire to. If you haven't gotten there yet - keep trying! Initially you'll feel this for maybe a second or two at a time - only the really great tzaddikim maintain this level of conviction on a constant basis ! )

B'Hatzlacha !