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I'll start with a broad answer and then drill down. A commonly repeated saying in the Israeli military is that each war must be fought for our survival; we cannot afford to lose even a single conflict as that would be our end. That perception stemmed from a lack in strategic depth (Israel is tiny), the concern that blood in the water would have attracted the rest of our regional adversaries into combat, and that our enemies sought our destruction rather than achieving limited strategic goals. Hence, Israel won each conflict because it was much more committed to getting a favourable outcome - our continued existence as a people supposedly depended on it.
This was, perhaps, true until after the Yom Kippur war of 1973, which arguably saw Israel closest to its strategic demise since our independence in 1948. After that fateful war, if you chart most of Israel's conflicts (1982 First Lebanon War, 2006 Second Lebanon War, two Intifadas, multiple campaigns in the Gaza strip), you'll see that they've weren't that classically classifiable as "victories".
That's partially because they were no longer wars for survival. They were bouts of combat waged against an asymmetrically weaker adversary, with no clear and sustainable victory usually possible without significant collateral damage. Did Israel win the 2006 Second Lebanon War? Perhaps, depends who you ask. While Hezbollah suffered extensive damage and strategic losses, Israel did not achieve the majority of its goals. The same applies to several of the conflicts with the Hamas, Islamic Jihad, etc.
To cycle back to the question - It is no longer as easy to say that Israel is able to win every single war with its Arab neighbours. Militarily, Israel still vastly outmatches any of its enemies in a conventional shooting war, especially with Syria crippled by civil war. But the wars themselves are no longer waged between the IDF and an Arab military, so results vary. Fighting insurgencies, terrorist organisations and entrenched militias is an entirely different process.
To wrap up the historical perspective, Israel indeed managed to achieve strategic success in each of its major conflicts up until the period described above for different reasons:
Indepdence War (1948-1949) - A massive recruitment effort, effective concentration of force, clever use of imported weaponry and combat against comparably ineffectual and unmotivated Arab forces (the British-trained Jordanian Legion a notable exception), all contributed to our success. By some historians' assessment, by the later stages of the war Israel's own forces were numerically close or even surpassed to those committed by Arab armies to the conflict.
Operation Kadesh (1956) - Well-defined, limited strategic goals kept Israeli forces on-mission. Significant logistical and combative support from French and British allies also enabled and cemented Israeli gains on the ground. Arguably most of all, achieving strategic surprise (the Egyptians realized they were being invaded too late) caused Egyptian forces to respond poorly to the ongoing campaign against them. There were some bloody battles, but shrewd and overly brave tactics by (then Colonel) Ariel Sharon were instrumental in quickly gaining ground.
Six Day War (1967) - Brashly and pre-emptively achieving strategic surprise with a massive aerial campaign against unwitting enemies completely altered the calculus of war. Entire airforces were wiped out on the ground, allowing the Israeli Air Force to operate with impunity and hammer at ground forces.
Yom Kippur War (1973) - A combination of holdout bravery, last-minute strategic wit, and of course critical supplies and armament from the United States all contributed to Israel's eventual victory of a war it was initially about to lose. Some claims are that the Syrians were so surprised that they have achieved their initial objectives that they just halted their advance, waiting further orders. This allowed beleaguered Israeli forces to regroup for effective counterstrikes.
