Rashi: Your beginning that passed was small, compared to your end, which will be very elevated.

Devar Eliyahu #1: Success comes very slowly to a Tzadik, like Chazal said about "Mi Zos ha'Nishkefah Kemo Shachar", then "Yafah ka'Levanah", then "Barah ka'Chamah", and after "Ayumah ka'Nidgalos." A human cannot receive success at once, just like he cannot receive the sun's light at once. After the darkness of night, first comes dawn, and it increases gradually.

Devar Eliyahu #2: Your beginning is in this world, and your end is in the world to come. It says in Bereishis Rabah (9) "Tov" is the Yetzer Tov; "Me'od" is the Yetzer ha'Ra. "Tov" is life; "Me'od" [is death]. It is not that Me'od is better than Tov. Rather, there are kinds of Tov - mostly or totally. Also the Yetzer ha'Ra and death are Tov. Your end will be very elevated - [the Yetzer ha'Ra] will make peace with you, like it says about Avraham "u'Matzasa Es Levavo Ne'eman." "Bi'Rtzos Hashem Darchei Ish Gam Oyvo Yashlim Ito" - the Yetzer ha'Ra.

Malbim: If you are a Tzadik, the afflictions that He brought on you without sin were to benefit your reward in your end!