[12] Therefore, my beloved, as you have always obeyed, so now, not only as in my presence but much more in my absence, work out your own salvation with fear and trembling;
[13] for God is at work in you, both to will and to work for his good pleasure. Phil 2:12-13 RSV
So how does one work out their own salvation?
Let's start out with a general example and then go to a biblical one.
Many projects are difficult and costly ones. Suppose we decide to start out on a plan to live a healthy life. It would involve giving up oily food, sweets, alcohol, smoking, gluttony, and taking up exercising and sleeping early.
Well some would think it too difficult and costly in terms of giving up some pleasures. It wouldn't matter if the end results were the same whether living healthy lifestyles or not, but the fact is that those who do make sacrifices live longer and better.
SO the situation is like this:
Option 1 Give up bad habits, begin good ones, live longer and better.
Option 2 Continue with bad habits, avoid good ones, live shorter and lower quality loves.
There is no magic bullet, no shortcuts, no pills that give you the result of Option 1.
The Israelites in the Exodus event lived a poor life, with less sacrifices in Egypt.
God offered them a better life, if they were willing to be loyal to Him, go through dangerous training, take risks.
They CHOSE the poorer option, they spoke out loudly to be taken BACK. They feared stepping out, taking risks. Even though God had demonstrated His ability and willingness to carry them to the final outcome.
In the New Testament, it says that many people feared joining the disciples:
Acts 5:12, 13
12At the hands of the apostles many signs and wonders were taking place among the people; and they were all with one accord in Solomon’s portico.
13But none of the rest dared to associate with them; however, the people held them in high esteem.
They too CHOSE the poorer option. They feared stepping out, taking risks.Even though God again had demonstated His ability and willingness to carry them to the final outcome.
This is why people refuse to become believers, because no one believes in a free lunch, that there is no gain without pain, although this fact is lost in unnecessarily jumping to other conclusions. Don´t let your theology get in the way of what the text actually says.