One of the most important parts of a character being accepted by readers is making sure that their actions stay true to themselves. Good or bad, they need to have some sort of internal logic. Sometimes the character can talk themselves into things they would never normally do. It all comes down to whether or not the action comes from a true character motivation, or are they simply justifying something to themselves?
An example might make it clearer. Say the character is feeling lonely and sitting in a bar. After a few drinks, the beer goggles kick in, and they decide that going home with this completely unknown person is a great idea. When they wake up, they look across at this new person in their life and decide that this is the person that is going to the one that will help them create a new better life. There is a big chance that this character is trying to justify an action that they are regretting. Do this too many times and the character comes across as dodgy. Their internal dialogue can help you work out where they are coming from. If it is all, “cause, really, if you think about it, they might be a millionaire and….” then the chances are, this is a justification. If they are saying to themselves, “I’ve never done this before but I am feeling too much to let it go” then maybe they have done something normally out of character, but they are staying true to themselves in the long run.