The Klausenberger Rebbe zt"l says Yaakov's ladder symbolizes the two approaches to self improvement. One way is to decide what you want to improve and map out a plan where you improve step by step until you reach your decided goal. This slow but steady journey has a good chance of success. If you work hard you will ultimately get there. That is what the pasuk says "V'Hinei Sulam Mutzav Artza V'Roishoi Magiah Hashamayma"; if the ladder is planted firmly on the ground, by climbing it one rung at a time you get you all the way as far as the heavens.
The second way is to go straight to the top and immediately begin to act
according to your loftiest ideals, like the perfect tzaddik. This method usually
ends rather quickly in miserable failure. To this the pasuk says "V'Hinei
Malachei Elokim"; if you want to be like a malach right away, then "Olim
V'Yordim Boi" you will rise very quickly but you will go right back down just as